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In the early days of telescopic astronomy, you could only focus on one small region of the sky at a time. Careful observations had to be done by hand, and so much of the breakthrough work centered around a particular object in the sky. A nebula or galaxy, quasar or pulsar. But over the years we’ve been able to build telescopes capable of capturing a wide patch of sky all at once, and with automation, we can now map the entire sky. Early sky surveys took years to complete, but many modern sky surveys can look for changes on the order of weeks or days. This ability to watch for changes across the sky is changing the way we do astronomy, and it is beginning to yield some interesting results. As a case in point, an infrared sky survey is revealing hidden stars we hadn’t noticed before.

In a series of papers published in the Monthly Notices of the Royal Astronomical Society, the authors have analyzed data from a decade-long survey called the Visible and Infrared Survey Telescope (VISTA). VISTA allows astronomers to keep an eye on hundreds of millions of stars at infrared wavelengths. In these works, the team combed through the observations to focus on about 200 stars that showed the most dramatic shifts in brightness. These transient changes are important because they can reveal the subtle dynamics of stars.

Artist’s impression of an eruption in the disc of matter around a newborn star. Credit: Philip Lucas/University of Hertfordshire

One goal of the studies was to look for very young stars. Stars in the earliest moments of transition toward becoming true fusion-powered stars. And within their selected stars they found 32 erupting protostars. All of them experienced a rapid increase of at least a factor of 40, and some brightened as much as a factor of 300. The outbursts lasted for months or years, and they seem to occur within the disk of matter surrounding the young stars. Based on the dynamics, these bursts can accelerate the growth of young stars, but they could also make it more difficult for planets to form. They refer to these turbulent protostars as squalling newborns.

The team also found a surprise. Deep within the center of our galaxy, they found 21 red giant stars with dramatic brightness changes. They turned out to be a new type of red giant known as old smokers. The center of our galaxy is rich with heavy elements, so these red giants have a high metalicity. As they age, they can cast off clouds of dust that can obscure the star for a time. So the star temporarily fades from view and then re-brightens as the clouds disperse. This discovery could change our understanding of how heavy elements are released into the galaxy to be used by new stars.

Reference: Lucas, P W, et al. “The most variable VVV sources: eruptive protostars, dipping giants in the nuclear disc and others.” Monthly Notices of the Royal Astronomical Society 582.2 (2024): 1789–1822.

Reference: Guo, Zhen, et al. “Spectroscopic confirmation of high-amplitude eruptive YSOs and dipping giants from the VVV survey.” Monthly Notices of the Royal Astronomical Society 582.2 (2024): 1769–1788.

Reference: Peña, Carlos Conteras, et al. “On the incidence of episodic accretion in Class I YSOs from VVV.” Monthly Notices of the Royal Astronomical Society 582.2 (2024): 1823–1840.

Reference: Guo, Zhen, et al. “Multiwavelength detection of an ongoing FUOr-type outburst on a low-mass YSO.” Monthly Notices of the Royal Astronomical Society 582.2 (2024): L115–L122.

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We do not yet know how, where, or why life first appeared on our planet. Part of the difficulty is that “life” has no strict, universally agreed-upon definition.

Normally this is not an issue, as the vast majority of life is most definitely alive, and only biologists interested in the extreme edges – viruses, prions, and the like – need to worry about precise classifications. But to study the origins of life we must, by necessity, examine a process that takes non-living matter and fundamentally changes it. Presumably this process happened in stages, with fits and starts along the way, and so the line between uncoordinated chemical reactions and the beginnings of vibrancy must be blurred.

It’s helpful here to present at least a simple working definition of life, not to rewrite the biology textbooks, but so that at least we can properly frame the discussion of life’s origins. And for those purposes a simple statement will suffice: life is that which is subject to Darwinian evolution. That is, life experiences natural selection, that unceasing pressure that chooses traits and characteristics to pass down to a new generation through the simple virtue of their survivability. If the trait contributes in some way, even circuitously, to the survivability of an organism and its ability to reproduce, it persists. All else is discarded (or, at best, gets carried unceremoniously along for the ride).

Earth is the only known place in the solar system, in the galaxy, in the entire universe where Darwinian evolution takes place.

To succeed at evolution and separate itself from mere chemical reactions, life must do three things. First, it must somehow store information, such as the encoding for various processes, traits, and characteristics. This way the successful traits can pass from one generation to another.

Second, life must self-replicate. It must be able to make reasonably accurate copies of its own molecular structure, so that the information contained within itself has the chance to become a new generation, changed and altered based on its survivability.

Lastly, life must catalyze reactions. It must affect its own environment, whether for movement, or to acquire or store energy, or grow new structures, or all the many wonderful activities that life does on a daily basis.

By interacting with its environment, making copies of itself, and storing information (like how to interact with the environment and make copies of itself), life can evolve, growing in complexity and specialization over geologic time, from humble molecules to conscious minds capable of peering into its own shrouded origins.

In the modern era, with billions of years of practice behind it, life on Earth has evolved a dizzying array of chemical and molecular machines to propagate itself – a menagerie so complex and interconnected that we do not yet fully understand it. But a basic picture has emerged. Put exceedingly simply (for I would hate for you to mistake me for a biologist), life accomplishes these tasks with a triad of molecular tools.

One is the DNA, which through its genetic code stores information using combinations of just four molecules: adenine, guanine, cytosine, and thymine. The raw ability of DNA to store massive amounts of information is nothing short of a miracle; our own digital system of 1’s and 0’s (invented because it’s much simpler to tell if a circuit is on or off than some stage in-between) is the closest comparison we can make to DNA’s information density. Natural languages don’t even earn a place on the chart.

The second component is RNA, which is intriguingly similar to DNA but with two subtle, but significant, differences: RNA swaps out thymine for uracil in its codebase, and contains the sugar ribose, which is one oxygen atom short of the deoxyribose of DNA. RNA also stores information but, again speaking only in generalities, has the main job of reading the chemical instructions stored in the DNA and using that to manufacture the last member of the triad, proteins.

“Proteins” is a generic catch-all term for the almost uncountable varieties of molecular machines that do stuff: they snip apart molecules, bind them back together, manufacture new ones, hold structures together, become structures themselves, move important molecules from one place to another, transform energy from one form to another, and so on.

Proteins have one additional function: they perform the job of unraveling DNA and making copies of it. Thus the triad completes all the functions of life: DNA stores information, RNA uses that information to manufacture proteins, and the proteins interact with the environment and perform the self-replication of DNA. This cycle allows living organisms to experience the gift of evolution.

And this cycle is, as I said, gloriously complex and obviously the result of billions of years of fine-tuning and refinement. The interconnected nature of DNA, RNA, and proteins means that it could not have sprung up ab initio from the primordial ooze, because if only one component is missing then the whole system falls apart – a three-legged table with one missing cannot stand.

The post The Improbable Origins of Life on Earth appeared first on Universe Today.

The James Webb Space Telescope, a collaborative effort between NASA, the ESA, and the Canadian Space Agency (CSA), has revealed some stunning new images of the Universe. These images have not only been the clearest and most details views of the cosmos; they’ve also led to new insight into cosmological phenomena. The latest image, acquired by Webb‘s Mid-InfraRed Instrument (MIRI), is of the star-forming nebula N79, located about 160,000 light-years away in the Large Magellanic Cloud (LMC). The image features a bright young star and the nebula’s glowing clouds of dust and gas from which new stars form.

The image above is centered on one of the three giant molecular cloud complexes – dubbed N79 South (S1) – a region dominated by interstellar atomic hydrogen that is ionized. The star is identifiable as the brightest spot in the image, surrounded by six large spokes of light that cross the image. The processed image uses many different colors to indicate different infrared wavelengths, with near-infrared light (7.7-10 microns) shown in blue, while mid-infrared wavelengths (10, 15, and 21 microns) are shown in cyan, yellow, and red (respectively).

The Tarantula Nebula as seen by the James Webb Space Telescope. Credit: NASA/ESA/CSA/STScI/Webb ERO Production Team.

This N79 nebula spans over 500 parsecs (1,630 light-years) in the largely unexplored southwest region of the LMC and is often regarded as the younger sibling to the Tarantula Nebula (aka. 30 Doradus). This nebula was imaged recently by Webb (see above), where combined light from varying wavelengths created a detailed image revealing many interesting features (like star-forming regions astronomers were not expecting to find). However, research suggests that for the past 500,000 years, N79 has had star formation efficiency more than twice that of the Tarantula Nebula.

Several other bright objects can be seen in the cloud, which are stars in the early stages of formation (aka. protostars) shown in great detail as layers of colorful wisps. Thanks to Webb‘s ability to capture longer and shorter wavelengths of infrared light, these latest image provides insight into the nebula’s star forming regions. Since shorter wavelengths are absorbed or scattered by dust grains, mid-infrared light reveals what is happening deeper inside the clouds (which include some young protostars). The image shows a distinct “starburst” pattern surrounding a bright object.

This is known as a “diffraction spike,” an artifact only visible around very bright and compact objects that arises from the design of a telescope’s mirrors. In this case, the six diffraction spikes extending from the center are due to the hexagonal symmetry of Webb’s eighteen primary mirror segments. Astronomers are particularly interested in star-forming regions because their chemical composition resembles that of nebulas observed when the Universe was only a few billion years old.

Unlike nebulae in the Milky Way today, star formation was at its peak during this time, producing particularly massive stars with low concentrations of metal and short-lived by current standards. By taking details images from N79 and similar nebulae, astronomers can compare and contrast star-formation rates to deep observations of distant galaxies in the early Universe.

Webb images of early galaxies shaped like surfboards and pool noodles. Credit: NASA/ESA/CSA

These latest observations by Webb are part of a program to study the evolution of circumstellar discs and envelopes around stars in formation over a wide range of mass and evolutionary stages. Webb‘s sensitivity will allow astronomers for the first time, to detect these planet-forming disks around stars of similar mass to that of our Sun and at distances comparable to that of the LMC (around 160,000 light-years). This will shed light on how planetary systems like our own formed and evolved, potentially providing clues as to where life may have also emerged in our galaxy.

Further Reading: ESA

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Our planet sits in the Habitable Zone of our Sun, the special place where water can be liquid on the surface of a world. But that’s not the only thing special about us: we also sit in the Galactic Habitable Zone, the region within the Milky Way where the rate of star formation is just right.

The Earth was born with all the ingredients necessary for life – something that most other planets lack. Water as a solvent. Carbon, with its ability to form long chains and bind to many other atoms, a scaffold. Oxygen, easily radicalized and transformable from element to element, to provide the chain reactions necessary to store and harvest energy. And more: hydrogen, phosphorous, nitrogen. Some elements fused in the hearts of stars, other only created in more violent processes like the deaths of the most massive stars or the collisions of exotic white dwarfs.

And with that, a steady, long-lived Sun, free of the overwhelming solar flares that could drown the system in deadly radiation, providing over 10 billion years of life-giving warmth. Larger stars burn too bright and too fast, their enormous gravitational weight accelerating the fusion reactions in their cores to a frenetic pace, forcing the stars to burn themselves out in only a few million years. And on the other end of the spectrum sit the smaller red dwarf stars, some capable of living for 10 trillion years or more. But that longevity does not come without a cost. With their smaller sizes, their fusion cores are not very far from their surfaces, and any changes or fluctuations in energy result in massive flares that consume half their faces – and irradiate their systems.

And on top of it all, our neighborhood in the galaxy, on a small branch of a great spiral arm situated about 25,000 light-years from the center, seems tuned for life: a Galactic Habitable Zone.

Too close to the center and any emerging life must contend with an onslaught of deadly radiation from countless stellar deaths and explosions, a byproduct of the cramped conditions of the core. Yes, stars come and go, quickly building up a lot of the heavy elements needed for life, but stars can be hundreds of times closer together in the core. The Earth has already suffered some extinction events likely triggered by nearby supernovae, and in that environment we simply wouldn’t stand a chance. Explosions would rip away our protective ozone layer, exposing surface life to deadly solar UV radiation, or just rip away our atmosphere altogether.

And beyond our position, at greater galactic radii, we find a deserted wasteland. Yes, stars appear and live their lives in those outskirts, but they are too far and too lonely to effectively spread their elemental ash to create a life-supporting mixture. There simply isn’t enough density of stars to support sufficient levels of mixing and recycling of elements, meaning that it’s difficult to even build a planet out there in the first place.

And so it seems that life would almost inevitably arise here, on this world, around this Sun, in this region of the Milky Way galaxy. There’s little else that we could conceivably call home.

The post The Galactic Habitable Zone appeared first on Universe Today.

In the beginning, the Universe was so hot and so dense that light could not travel far. Photons were emitted, scattered, and absorbed as quickly as the photons in the heart of the brightest stars. But in time the cosmos expanded and cooled to the point that it became transparent, and the birthglow of the Big Bang could traverse space and time for billions of years. We still see it as the microwave cosmic background. As the Universe expanded it grew dark, filled only with warm clouds of hydrogen and helium. In time those clouds collapsed to form the first stars, and light again filled the heavens.

None of the stars we see today were among those first stars. Modern stars are rich with elements such as carbon and iron. Heavier elements only formed in stellar cores and other astrophysical processes. The first stars we made only of hydrogen and helium. They must have been massive beasts, with fleeting lives that ended in brilliant supernova explosions. Only their remnants remain. There have been several deep sky searches for these first stars, but we have so far not seen them. There is some indirect evidence of them in the distant Universe, but we have not yet seen their light. Now a new study argues that the Nancy Grace Roman Space Telescope might capture their dying radiance.

How a TDE of a first-generation star might be observed. Credit: Chowdhury, et al

Formally known as the Wide-Field Infrared Survey Telescope (WFIRST), The Roman Space Telescope is scheduled to launch in late 2026. Like the JWST, it will observe the cosmos in infrared, but Roman will have a wider field of view. This will better enable it to find the highly redshifted light of the first stars. However, the authors note that given the short lifespan of these first stars, Roman will not likely observe them directly. They instead propose looking for evidence of these stars as they are consumed by a black hole.

Specifically, the team proposes looking for what are known as Tidal Disruption Events (TDEs). When a star passes near a black hole, the gravitational tidal forces of the black hole can rip the star apart. As a result, the remnants of the star can be strewn across a large arc. This process takes time and creates a stream of heated gas. The authors modeled the emission spectra of this gas for a first-generation star and found they have a unique signature that lasts for a considerable amount of time. Much of the light from such a TDE would be emitted in the strong ultraviolet, but since they would occur at a cosmic redshift of about z = 10, the light we see would be shifted to the infrared, making it observable by JWST and the Roman Space Telescope.

The authors note that the rate at which TDEs occur for first-generation stars depends on several factors, but given reasonable estimates Roman could expect to see tens of these TDEs per year. So in a few years, we might finally be able to capture the last dying light of the first stars.

Reference: Chowdhury, Rudrani Kar, et al. “Detecting Population III Stars through Tidal Disruption Events in the Era of JWST and Roman.” arxiv preprint arXiv:2401.12752 (2024).

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We live in an age of renewed space exploration, colloquially known as Space Age 2.0. Unlike the previous one, this new space age is characterized by inter-agency cooperation and collaboration between space agencies and the commercial space industry (aka. NewSpace). In addition to sending crews back to the Moon and onto Mars, a major objective of the current space age is the commercialization of Low Earth Orbit (LEO). That means large constellations of satellites, debris mitigation, and plenty of commercial space stations.

To accommodate this commercial presence in LEO, Sierra Space has developed the Large Integrated Flexible Environment (LIFE) habitat, an inflatable module that can be integrated into future space stations. As part of the Commercial Low Earth Orbit Development Program, NASA, Sierra Space, and ILC Dover (the Delaware-based engineering manufacturing company) recently conducted a full-scale burst pressure test of their LIFE habitat. The test occurred at NASA’s Marshall Space Flight Center in Huntsville, Alabama, and was caught on video (see below).

Commercial space has become one of the fastest-growing businesses on Earth. In the past decade, the space economy has expanded by over 60% and is currently valued at around $400 billion. This is expected to grow considerably in the coming years as launch services increase, small satellites (CubeSats) become more affordable, and orbital stations are built. As the International Space Station (ISS) nears retirement, these commercial stations will provide opportunities for research and development, orbital manufacturing, and space tourism.

Sierra Space, the developer of the Dream Chaser reusable spaceplane, has demonstrated its commitment to the commercialization of LEO and the NewSpace economy. The first iteration of their inflatable habitat, LIFE 1.0, measures 6 meters (~20 feet) long and 9 meters (~30 feet) in diameter and can be launched using conventional rockets and inflates once in orbit. With a volume of 285 cubic meters (over 10,000 ft3), it can accommodate four astronauts, with additional room for science experiments, exercise equipment, and Sierra Space’s Astro Garden® plant-growing system.

The purpose of a burst pressure test is to gauge the structural tolerances of a component, be it a fuel tank or an inflatable module. The data gained from this test will assist engineers in simulating how the module will fare in the vacuum of space. Once development and testing are complete, the module will be used on commercial space stations like Orbital Reef, a collaborative effort between Blue Origin and Sierra Space. Future versions, like Life 2.0 and 3.0, will offer additional volume and be able to accommodate larger crews and more science operations.

According to their National Strategic Plan (released in 2022), one of NASA’s strategic goals is to develop a human spaceflight economy in collaboration with the NewSpace industry. In 2021, as part of a Commercial LEO Destinations (CLDs) project, NASA Space Act Agreements with three companies to design commercial space stations. This includes the Orbital Reef proposed by Blue Origin and Sierra Space, the Starlab space station by Nanoracks LLC, Voyager Space, Lockheed Martin, and Northrop Grumman’s free flyer commercial space station.

Starlab, from Nanoracks, Voyager Space, and Lockheed Martin – a continuously crewed, free-flying commercial space station in low-Earth Orbit. Credits: NanoRacks/Lockheed Martin/Voyager Space

As per NASA’s plan, creating a human spaceflight economy will ensure continued research and development in space while “allowing NASA to focus Government resources on the challenges of deep space exploration through Artemis.” Another goal is to maintain the legacy of the ISS long past its retirement:

“Since its inception, industry, academia, and our international partners have used the International Space Station (ISS) as a testbed for research and the development and maturation of state-of-the-art systems that increase access to space. NASA is supporting new space stations from which we and other customers can purchase services and stimulate the growth of commercial human spaceflight activities. As commercial LEO destinations become available, we intend to implement an orderly transition from current ISS operations to these new commercial destinations.”

Further Reading: Sierra Space

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Although our Moon formed 4.5 billion years ago, it’s still evolving. The interior continues to cool and its orbit is slowly changing. As a result, the Moon has lost 150 feet of its circumference. That shrinkage contributes to near-constant moonquakes, and those trigger landslides and other surface changes. The Moon is currently uninhabited, but all that activity threatens future Artemis landing sites and missions at the South Pole.

In a recent paper, planetary scientists point out that the potential of strong seismic events from active thrust faults should be a top consideration when NASA and other agencies are planning permanent outposts on the Moon. This is particularly true as the Artemis mission planners plot exploration of the South Pole. “Our modeling suggests that shallow moonquakes capable of producing strong ground shaking in the south polar region are possible from slip events on existing faults or the formation of new thrust faults,” said the study’s lead author Thomas R. Watters, a senior scientist emeritus in the National Air and Space Museum’s Center for Earth and Planetary Studies. “The global distribution of young thrust faults, their potential to be active, and the potential to form new thrust faults from ongoing global contraction should be considered when planning the location and stability of permanent outposts on the Moon.”

The Moon is particularly vulnerable to the large-scale effects of moonquakes. That’s because its surface is very brittle and easily broken up during a quake. One of the strongest quakes in lunar history occurred in the 1970s and lasted for hours. Such a lengthy event does quite a bit of damage to the lunar surface. So, even a light moonquake could cause significant damage via landslides.

Our Shaky, Shrinking Moon

Moonquakes generally happen within a hundred miles or so of the lunar surface. On Earth, that might result in a fairly mild quake. But, since the Moon’s surface is so brittle, the effects of those “shakes” are much more noticeable. According to Nicholas Schmerr, a co-author of the paper and an associate professor of geology at the University of Maryland, this means that shallow moonquakes can devastate hypothetical human settlements on the Moon.

“You can think of the Moon’s surface as being dry, grounded gravel and dust,” he said. “Over billions of years, the surface has been hit by asteroids and comets, with the resulting angular fragments constantly getting ejected from the impacts,” Schmerr explained. “As a result, the reworked surface material can be micron-sized to boulder-sized, but all very loosely consolidated. Loose sediments make it very possible for shaking and landslides to occur.”

An LROC NAC mosaic of the Wiechert cluster of lobate scarps in Moon’s south pole region, left pointing arrows). A scarp crosscuts a small (?1 km) degraded crater (right-pointing arrow).

Quakes affect every part of the lunar surface. Global compressional stresses deform the surface, forcing splits and cracks to occur. These scarps—steep slopes and cliffs—exist everywhere there. In their paper, the team suggests that many are close to the epicenters of geologically recent quakes. And the regions where they occurred could still be active today. That includes the lunar South Pole.

Risks to Artemis

The team led by Watters examined data and images of the lunar South Pole and linked faults there to a major moonquake in the 1970s. The region is filled with scarps, which are prime evidence for moonquakes. Although they conclude that some regions in the area are probably safe enough for the Artemis missions, others are not. The team’s computer models show that the most dangerous areas are vulnerable to landslides triggered by seismic shaking. They continue to map the Moon and track its quakes to identify the riskiest areas for Artemis astronauts to land.

A mosaic of Shackleton Crater at the Moon’s south pole region. It shows a portion of an interior wall and floor, with arrows pointing to boulder falls likely created during seismic shaking during a moonquake. Image courtesy: NASA/KARI/ASU

That mission could take place by the end of the decade, when NASA hopes to establish long-term habitations for research and exploration. Schmerr points out that the risks to safety from even the slightest quakes can’t be overestimated. “As we get closer to the crewed Artemis mission’s launch date, it’s important to keep our astronauts, our equipment, and infrastructure as safe as possible,” Schmerr said. “This work is helping us prepare for what awaits us on the moon—whether that’s engineering structures that can better withstand lunar seismic activity or protecting people from really dangerous zones.”

The Artemis missions essentially mark NASA’s return to human exploration of the Moon. The idea is to collaborate with both commercial partners and international agencies to make this happen. Teams of lunar astronauts will establish an Artemis Base camp, and depend on a lunar gateway to connect the mission to Earth. Eventually, what they learn there will inform the first human missions to Mars.

For More Information

The Moon is Shrinking, Causing Landslides and Instability in Lunar South Pole
Tectonics and Seismicity of the Lunar South Polar Region
Artemis

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As April’s ‘Great North American Eclipse’ nears, here’s a look at eclipses in time and space.

It comes around every total solar eclipse, and I fully expect to hear it trotted out once again this year, leading up to the Great North American eclipse on April 8th, 2024.

It’s often repeated (usually around the time leading up to a total solar eclipse) that the syzygy of the Earth, Moon and Sun is special, allowing totality to occur. To be sure, eclipses are extraordinary and spectacular events, and standing in the shadow of the Moon during totality is a spectacle that shouldn’t be missed.

But just how rare are the circumstances we witness on Earth during totality across time and space?

The path of totality across North America on April 8th, 2024. Credit: Michael Zeiler/The Great American Eclipse How Rare are Eclipses?

The Moon’s orbit intersects the ecliptic at two points, known as its ascending and descending nodes. We see lunar and solar eclipses on Earth when these nodes line up with the Sun (during a solar eclipse) or the Earth’s shadow (during a lunar eclipse). The Moon’s path is tilted just over 5 degrees versus the ecliptic plane. This means that most of the time, the Moon misses the Sun, and the Earth’s shadow. If it wasn’t tilted, an even more unique situation would occur. In this case, we’d see two eclipses (one lunar and one solar) occurring every synodic period or roughly just under once a month. As it is, eclipses worldwide happen in seasons or about twice a year as the nodes line up, with a solar and lunar eclipse about two weeks apart.

How a totality occurs. Credit: NASA

The precision-looking fit of the Moon over the Sun seen during totality is due to geometry. The Sun is about 400 times farther away from the Earth than the Moon, and 400 times as large in terms of physical diameter. But this is only approximate, and only true for our current epoch.

Geometry for lunar and solar eclipses, with the true scale of the Moon’s umbra during totality (bottom). From The Universe Today’s Ultimate Guide to Viewing the Cosmos. A Receding Moon

In fact, we know from the retro-reflectors placed on the Moon by Apollo astronauts that the Moon is moving away from us at 3.8 centimeters per year. About 600 million years from now, the last total solar eclipse will occur as seen from the Earth. Likewise, about a billion years in the past, the first brief annular solar eclipse must have occurred.

The apparent size of the Sun and Moon also vary slightly from one eclipse the the next. This ranges around half a degree (30 arcminutes) by few arcminutes (‘). This occurs as the Earth travels from perihelion to aphelion, and the Moon travels from perigee to apogee. When the Moon is too small to cover the Sun, a ‘ring of fire’ annular solar eclipse occurs.

The value difference for the apparent size of the Sun ranges from 31.6′ to 32.6′, and the Moon is 29.3′ to 34.1′. During the April 8th total solar eclipse, the Sun will be an apparent 31′ 57″ across. The Moon will be slightly larger, at 33′ 37″ across. This will yield a generous maximum totality of 4 minutes and 28 seconds in duration, as seen from near Nazas, Mexico .

A Fortunate Epoch

Even now in our current 5,000-year epoch, annulars are already more common, at 33.2% to 26.7% versus totals. The remainder are partials and rare hybrid annular-total eclipses.

“I found that whenever I use the phrase ‘cosmic coincidence’ to describe our current good fortune in the distance/diameter ratios favorable for a tight occultation of the Moon and Sun, almost predictably some of the responses will be ‘there are no coincidences,’ or ‘divine provenance,'” Eclipse chaser and cartographer Michael Zeiler told Universe Today. “I respond that often coincidences are true! We are simply lucky to live within the evolution of our solar system to witness total solar eclipses.”

Looking Out Across the Solar System

To be sure, solar eclipses do occur throughout the solar system. It’s all a matter of perspective, and literally knowing where and when to stand. New Horizons saw the Sun pass behind Pluto in 2015 (a sight no human eye has ever witnessed). Rovers on Mars have caught strange potato-shaped annular eclipses (or more properly, transits) courtesy of Deimos and Phobos.

Deimos transits the Sun, as seen by NASA’s Perseverance Rover of Sol 1037 (January 20th, 2024). Credit: NASA/JPL Image processing: Simeon Schmaub

These robotic observations of the Martian moons aren’t just pretty pictures. They also also researchers to refine and pin down the exact orbits of both Phobos and Deimos. This is handy, as Japans Martian Moons Explorer is headed to the pair in 2026.

What’s more, Phobos is doomed to crash into Mars millions of years from now… at some far off date, it will briefly be close enough to totally eclipse the Sun as seen from the Martian surface. If humans are on Mars on November 10th, 2084, they can witness an uber-rare, transit featuring Phobos, the Earth and the Moon.

Eclipses and the Curious Case of the Jovian Moons

Of course, none of these are are precise fits in terms of the eclipsing body versus the Sun. There is, however, another place in the solar system you could stand on a solid surface and witness totality similar to what’s seen on Earth. (Be sure to pack your space suit). Jupiter’s major moons produce eclipses very analogous to those seen on Earth as they pass one in front of the other. This happens in cycles that occur during what’s known as mutual eclipse-transit season. This happens when the major Galilean moons of Io, Europa, Ganymede and Callisto mingle as seen from our perspective.

Europa as seen from the surface of Callisto is a particularly good baseline ‘fit’. Europa is about 1/450th the size of the Sun, which is also 450 times farther away at certain points along its orbital path… not all that different than eclipse circumstances here on Earth. These events are faster, lasting only a few dozen seconds at most. Mutual transit-eclipse season occurs twice every Jovian orbit, or every six years. The next cycle resumes in 2026.

Io casts its shadow on Ganymede in 2009. Image credit: Christopher Go. A Twice a Decade Transit Season

We noticed this similarities of Jovian versus terrestrial eclipses while writing an article on mutual eclipse season in 2015. To be sure, eclipse seasons on the Earth tend to be biannual, while seasons in the Jovian system occur less frequently, about twice a decade. More distant moons may see similar celestial sights, but for now, my future plans for building an eclipse viewing hotel and resort are pegged for the surface of Callisto.

Bill Kramer also did a fascinating look at eclipses throughout the solar system from a few years back, posted on his Eclipse-Chasers website.

The Hunt for ‘Exo-Eclipses’

So, what does this all say for eclipses beyond our solar system? Well, as of writing this, there are 5,506 exoplanets known… but claims of any ‘exomoons’ orbiting them remain controversial. Even the best known cases—such as the contentious recent Kepler-1513 b exomoon claim—still have very wide distance and diameter perimeters to say if good-fit eclipses are possible. Still, as the menagerie of extra-solar worlds grow and good exomoon candidates are found, we might yet be able to say with some authority just how common ‘exo-eclipses’ are very soon.

Perhaps, human astronauts will one day witness these far-flung eclipses. Imagine standing on the Earthward face of the Moon during a total lunar eclipse, and witnessing ‘a thousand sunsets’ as the Earth eclipses the Sun. For now, I’d wager that ideal tight-fit eclipses aren’t all that uncommon when you take into account the vast expanse of time and space… but totality over an expanse where life has evolved to enjoy it might be rare indeed.

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All modern life shares a robust, hardy, efficient system of intertwined chemicals that propagate themselves. This system must have emerged from a simpler, less efficient, more delicate one. But what was that system, and why did it appear on, of all places, planet Earth?

This is the central question of abiogenesis, the generation of life from not-life. We do not yet have an answer to that question, but we do have a collection of curious clues and brilliant hypotheses that might lead us in the right direction.

First, the chemistry. All proteins on Earth are made from just 22 amino acids. Those amino acids require abundant amounts of organic molecules – the most basic building blocks of life. Astronomers have detected organic molecules, and even some amino acids, scattered throughout space, from the depths of interstellar gas clouds to the fragile meteoroids that wander the solar system. So it’s natural to assume that our planet, as it coalesced from the maelstrom that surrounded our infant Sun, was born with the right ingredients…but surely they couldn’t survive the initial formation of our planet, when it was still molten from the countless collisions that lead to its development.

Instead, these organic compounds must have been delivered to us well after the planet cooled and solidified. Astronomers believe that the first few million years in the solar system was a quite unfriendly time. Even after the protoplanetary disk around the Sun evaporated and the eight major planets of the system emerged victorious over their rivals, fragments and debris still littered the orbital lanes. Impact after impact struck each of the planets, with new rounds triggered by gravitational rearrangements of the giant outer worlds as they settled into stable, permanent configurations.

We still see the scars of that youthful violence today, visible on the sterile vacuum surfaces of the Moon and Mercury.

But in that violence came a chance for life. Fresh water, delivered by countless cometary impacts, replenished what the Earth lost during its molten state. And with that water, organic compounds rained onto the surface. Here too we see yet another delicate balancing act. If the Earth had been struck too few times, we might not have been wealthy enough in molecular resources to begin the ascent to life. If too many had come, however, the persistent heat of the impacts would have boiled our oceans and sent any nascent life scattering into interplanetary space.

We were lucky. Somewhere life gained a foothold. The earliest undisputed fossil evidence for life sets the clock as early as 3.5 billion years ago. More speculative evidence – again, this work becomes exceedingly difficult the farther back into the past we peer, because the earliest life was not much different than the non-living chemical reactions that preceded it, so it’s difficult to tell if some molecular imprint in a rock is the fossil of a living creature or merely some manifestation of exotic chemistry, and if there’s even a difference between them – suggests that life started as early as 4.5 billion years ago. That alone is surprising, given the hellish conditions our planet was experiencing at the time, with some scientists arguing that our world wasn’t even habitable until some 500 million years later.

But somewhere, in some quiet place, the magic happened. A chance group of molecules and chemical reactions began storing information, began self-replicating, and began catalyzing reactions. Some biologists suspect that it was deep-sea hydrothermal vents, which spew organic-rich molecules into their surroundings. Or perhaps it was in tidal pools, which provided a natural rhythm that would turn into the cycles of life. Or maybe hot springs, or even underground.

It may have happened more than once and in more than one way, but it appears from all available evidence that as soon as life could arise, it did arise.

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There have been numerous robotic space missions reach the end of their operating life over the years and for a multitude of reasons. Be they catastrophic failure or a scheduled end but I must say one that has recently made me a little sad is the demise of the Ingenuity helicopter on Mars. It sustained damage after its recent flight and can now no longer fly. In a mission that was supposed to complete five flights in 30 days, the plucky little helicopter completed 72 flights over three years! 

The Ingenuity helicopter’s historic journey began on 18 February 2021 when it arrived on Mars. It was transported as part of the Mars 2020 mission which included the Perseverance rover too. Ingenuity had been built by NASA Jet Propulsion Laboratory with involvement from AeroVironment Inc., Qualcomm, SolAero and Lockheed Space. The task for Ingenuity was a simple one, to demonstrate the technology to perform flights on another world.

Perseverance Rover (Credit : NASA)

Once setup for flight, it stood 0.49 metres tall and its rotors had a span of 1.2 metres. This may seem a large wingspan in comparison to drones here on Earth but they needed to be this long to achieve flight on Mars. The lower atmospheric density meant that larger rotors were needed to produce the required amount of lift. The blades were to spin at a rate of 2,400 revolutions per minute but there were two drives that would spin one set of blades clockwise and the other counterclockwise. At the very top, above the rotors was a solar panel to charge its batteries, there was a wireless communication system and of course navigation sensors and cameras. 

The first flight took place on 19th April in the same year proving for the first time that powered flight was possible on another world. In the flights that followed, the operations team tested its systems and used it to scout out locations for the Perseverance rover to explore in detail.  

The plan was for Ingenuity to only last 3 days during the spring of 2021 and so the team had to overcome a number of obstacles during its extended mission. The teams had to develop winter operating procedures so that Ingenuity could survive the long cold nights. They upgraded the systems giving it the ability to choose its own landing sites and even had to clean itself after dust storms.

On the 18th January this year, the team had to identify the location of Ingenuity since it had to make an emergency landing on a previous flight. As planned, the helicopter lifted off to an altitude of 12 metres to survey the surrounding terrain and hovered for 4.5 seconds before descending again at a velocity of 1 metre per second.  Unfortunately and for unknown reasons, there was a communication failure at an altitude of about 1 metre.  Investigations the following day revealed there was damage to one of the rotor blades rendering the helicopter incapable of further flight. 

The team are now trying to identify the cause of the failure while they perform tests on the systems one last time and download the last images stored onboard. Too often we hear of missions that go wrong but Ingenuity was a fabulous example of a mission that went way beyond its expectations giving us so much more than was ever hoped for. 

Source : After Three Years on Mars, NASA’s Ingenuity Helicopter Mission Ends

Link :

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What were you doing last Saturday? As it turns out, I was doing something rather unexciting… Trying to fix my washing machine (I did – in case you are interested). At the same time, Hungarian geography teacher by day and asteroid hunter by night Krisztián Sárneczky was out observing and detected a small asteroid which it transpired was on a collision course with Earth! 

Spotting asteroids is a tricky business. Not least because they are typically dark in colour against a very black sky but the sky is quite a big place and spotting a tiny dark object against a massive black sky is worse than looking for a needle in a haystack!

Unperturbed by the statistics and likelihood of actually discovering one, Sárneczky regularly scours the sky looking for asteroids and supernova at the Konkoly observatory in Budapest, Hungary.  He was engaged in this very task last Saturday night (20th January) at 22:48 CET (21:48 UT) when he spotted a new asteroid using a 0.6m Schmidt Telescope. Any discovery of this sort requires swift action to get the data over to the Minor Planet Center (MPC) who co-ordinate observations from astronomers around the World. 

Sárneczky only had three observations when he submitted the data but continued to observe and over the course of the following minutes secured four more observations which he passed over realising it was heading straight for Earth. The actions that follow any such discovery like this are that the MPC alert others for follow up observations. Astronomers and automated impact monitoring systems including the European Space Agency’s wonderfully named ‘MeerKAT’ system sprang into action and more observations came in. 

A radio image of the central portions of the Milky Way galaxy composited with a view of the MeerKAT radio observatory. Radio bubbles and associated vertical magnetized filaments can be seen. Courtesy: MeerKAT/SARAO/Oxford University/Heywood

With more data, came more accuracy and thankfully the knowledge the the impactor was only about a metre across and due to impact just west of Berlin in Germany. It is not unusual for asteroids of this size to hit Earth indeed, we get them every couple of weeks but they generally burn up in the atmosphere and pose no threat. Larger asteroids that do pose a threat are thankfully much rarer. Larger objects are also easier to spot so the majority have already been spotted and are already being tracked but there are automated searches and individuals like Sárneczky who are always on the look out.

The asteroid, which is now known as 2024-BX1 hit the Earth’s atmosphere just a few hours after discovery at 01:32 CET (00:32 UT) on Sunday morning the 21st January, 50km to the west of Berlin. It burned up, leaving a fabulous streak across the sky which people witnessed as a fireball even being spotted over here in the UK.

Worryingly it is actually quite an unusual thing for asteroids to have been discovered before they impact our atmosphere. Only eight have been spotted with the first back in 2008. The difficulty of course is to find them early enough to give us time to understand their trajectory and size to understand what level of threat they pose to us. I should add there are no known asteroids on a collision course with Earth  and fortunately there are people like Sárneczky and a number of automated search systems out there on the lookout for the next one. 

Source : Asteroid 2024 BX1 spotted three hours before impact

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Now we know why Japan’s lunar lander wasn’t able to recharge its batteries after touching down on the moon last week: The spacecraft appears to have tumbled onto its side, with its solar cells facing away from the sun.

The good news is that the Smart Lander for Investigating Moon, or SLIM, achieved its primary mission of setting down within 100 meters (330 feet) of its target point — and that the mission’s two mini-probes, which were ejected during SLIM’s descent, are working as intended.

Scores of images were taken before and after landing. One of the pictures. captured by a camera on the ball-shaped LEV-2 mini-probe, shows the lander sitting at an odd angle with its thrusters facing upward and its solar cells facing westward.

To conserve battery power, mission managers at the Japan Aerospace Exploration Agency shut down SLIM after the probes transmitted the imagery they collected. But there’s still a chance that the sun’s shifting rays could provide enough power to allow for further operations in the week ahead.

JAXA project manager Shinichiro Sakai accentuated the positive as he showed off a photo from the mission. “Something we designed traveled all the way to the moon and took that snapshot,” he said. “I almost fell down when I saw it.”

Scientists gave fanciful names to the rocks visible in the pictures — including St. Bernard, Bulldog and Toy Poodle.

Mission managers analyzed the imagery as well as spacecraft data to figure out what happened to SLIM. One of the lander’s two main engines apparently malfunctioned during the descent, and the other main engine tried to compensate. The mission team said that the spacecraft touched down about 55 meters east of the target point near Shioli Crater — and that SLIM could have landed within 4 meters of the target if both engines had been working.

Despite the setbacks, Sakai said the “Moon Sniper” landing came close enough to rate the mission a success. “We demonstrated that we can land where we want,” he said. In the past, most interplanetary landing missions have had to plan for wider margins of error. NASA’s Perseverance rover, for example, targeted a 7.7-kilometer-wide landing ellipse in 2021.

SLIM’s landing site is illuminated by sunlight until Feb. 1, and researchers are hoping that as the sun heads toward the west in lunar skies, the lander’s solar cells will soak up enough light to allow for the resumption of powered operations. If the lander can be revived, the first priority will be to conduct high-resolution spectroscopic observations of the surroundings.

But SLIM’s time is extremely limited: During the 14 dark days that follow lunar sunset, falling temperatures are expected to put the lander into a deep freeze. “SLIM is not designed to survive a lunar night,” Sakai said.

Even if the lander can’t be revived, the ability to put a robotic spacecraft safely on the moon marks a triumph for Japan’s space effort. Only four other countries — the United States, Russia, China and India — have achieved similar feats.

The post Japan’s Moon Lander Is Lying On Its Side After Hitting Its Target appeared first on Universe Today.

In the next fifteen years, NASA, China, and SpaceX will make the next great leap in space exploration by sending the first crewed missions to Mars. This presents many challenges, not the least of which is distance. Even when they are closest to each other in their orbits (aka. when Mars is in Opposition), Mars can still be up to 55 million km (34 million mi) from Earth. Using conventional propulsion (chemical rockets), a one-way transit can last six to nine months, which works out to a total mission time (including surface operations) of about three years.

That’s a very long time for people to be in microgravity, not to mention exposed to solar and cosmic radiation. To address this, NASA is investigating advanced propulsion methods that will reduce transit times and hibernation technologies that will allow crews to sleep through most of their voyage. This year, the NASA Innovative Advanced Concepts (NIAC) program selected the Studying Torpor in Animals for Space-health in Humans (STASH) experiment, a new method for inducing torpor developed by Ryan Sprenger and colleagues at the California-based biotechnology firm Fauna Bio Inc.

Today, there is a growing field in biotechnology where unique mammalian traits are being investigated and used to develop novel therapeutic agents. This includes the phenotype of hibernating mammals, which are currently being investigated for human health applications here on Earth. But as Ryan Sprenger and his team indicate in their proposal, these benefits also have applications for space exploration, which include mitigating the associated physical and mental health risks. And for long-duration missions to Mars and beyond, these risks are legion!

Ongoing research aboard the International Space Station (ISS), such as NASA’s famous Twin Study, has shown how extended periods in microgravity can take a significant toll on human health. This includes muscle atrophy, bone density loss, and effects on organ function, eyesight, cardiovascular health, and the nervous system. Another major issue is the need for resupply, which can be accomplished in a matter of hours for the ISS but would take six to nine months where crewed missions to Mars are concerned.

There’s also the prospect of spending months in a cramped spacecraft, which is bound to take a toll on the crew, and the problem of waste management along the way. Under these circumstances, NASA and other space agencies are considering placing crews in a state of hibernation for their journey. This would ensure that the crew arrives at Mars in a healthy state and is prepared for the months of surface operations that will follow. The essential feature, writes Spenger and his team, is “an energy-conserving state called torpor” that involves a deep reduction in metabolism.

To this end, they have proposed an experiment called “Studying Torpor in Animals for Space-health in Humans” (STASH), a hibernation laboratory for use aboard the ISS. This unit is being developed in collaboration with the BioServe Space Technologies College of Engineering and Applied Science at the University of Colorado Boulder to be integrated into the Space Automated Biological Laboratory (SABL). The experiment consists of two chambers that will house test rodents, maintaining temperatures as low as 4° C (39° F) to induce torpor.

The system will have instruments that measure the animals’ metabolism in real-time by monitoring their oxygen consumption, body temperature, and heart rate. The short-term goals of the STASH include investigating hibernation science in a microgravity environment, which includes determining if hibernation provides the expected protection against bone and muscle loss. The medium-term goals include testing bioactive molecules that mimic the gene expressions of hibernation and evaluating methods of inducing synthetic torpor.

The long-term goal, they write, is to develop applications for deep space missions:

“[D]uring a crewed mission to Mars, human synthetic torpor could act as a relevant countermeasure that would change everything for space exploration, mitigating or eliminating every hazard included in NASA’s RIDGE acronym for the hazards of space travel: Space Radiation, Isolation and Confinement, Distance from Earth, Gravity Fields, and Hostile/Closed Environments.”

As Sprenger and his colleagues noted, there is a critical gap in our understanding of hibernation and its potential applications for human spaceflight. Currently, the infrastructure needed to study torpor in space does not exist, and hibernation in microgravity has not yet been studied. In this respect, STASH will serve as a pathfinder, laying the groundwork for future studies that could lead to hibernation systems for deep space missions. With Phase I development funding secured through the NIAC program, the team is excited to take the first steps. As they summarized in their proposal:

“Research performed using STASH will be an essential first step toward acquiring fundamental knowledge about the ability of hibernation to lessen the health risks of space. This knowledge will inform the development of both biomimetic drug countermeasures and the future infrastructure needed to support torpor-enabled human astronauts engaged in interplanetary missions. We feel that STASH is the epitome of the high-risk, high-reward projects for which NIAC was established.”

Further Reading: NASA

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In November 2023, the monster iceberg A23e finally dislodged from the seafloor after being grounded and stuck there for 40 years. A series of recent satellite images show that the mighty iceberg is now heading away from Antarctic waters, seeking fame and fortune in the high seas. A23a measures 4,000 sq kilometers in area and is over 280 meters thick, and is currently the world’s largest iceberg. Its first path will follow the Antarctic Circumpolar Current, heading towards South America.

Tiny Elephant Island, an ice-covered, mountainous island off the coast of Antarctica seen in the image above, has an area of only 215 sq km.

ESA’s Copernicus Sentinel-1 satellite and NOAA’s Advanced Microwave Scanning Radiometer 2 (AMSR2) onboard the GCOM-W1 satellite have been keeping an eye on the moving behemoth, which appears to be driven by winds and currents. Scientists estimate it is moving at a rate of about 4.8 km (3 miles) each day, but that could change as it enters the currents.

Iceberg A23a separated from the Fichner-Ronne ice shelf in West Antarctica in 1986. It was so big that it became grounded, stuck to the seafloor, and remained in position for 40 years. ESA said it is not unusual for icebergs to become grounded, but over time they shrink enough to become unground and float.

An animation from Copernicus Sentinel-1 images shows iceberg A23a’s movements from 2 November 2023, 14 November 2023 and 26 November 2023. Credit: ESA.

A23a is a biggie, but it’s not the largest ever. It is only about one-third the size of the biggest iceberg in recorded history, B-15 which calved off of Antarctica’s Ross Ice Shelf in 2000. The B-15 iceberg covered more than 10,878 square km (4,200 square miles) when it broke away, according to NASA’s Earth Observatory. B-15 has since fractured into numerous smaller bergs, and most have melted away.

Like many icebergs before it, A23a is being propelled it towards the South Atlantic along a trajectory commonly referred to as ‘iceberg alley’, because of the Antarctic Circumpolar Current.

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It’s been a big week for Chinese space exploration. First a successful test flight of Zhuque-3 and this week we learned of their plans to explore the Moon’s South Pole. Previous missions have even returned samples to Earth but the Chinese landers have yet to explore more southerly areas of the Moon. Chang’e-6 is due to launch in a few months to collect samples from the far side of the Moon while Chang’e-7 launches in 2026 to the Moon’s south pole. 

It’s an exciting prospect to see China continuing their exploration of the Moon. in a paper recently published, the team from the Natinoal Space Science Centre under the Chinese Academy of Sciences and China Lunar Exploration and Space Engineering Center (sorry, that is a mouthful) explore the scientific goals and the payloads required to reach those targets. One of the key goals is to explore the craters around the south pole to study the water ice lurking in the shadows. 

Scientists have wondered about the existence of water on the Moon for decades but it wasn’t confirmed until 2020. Data returned by NASA’s SOFIA mission finally confirmed that there was water on the surface of the Moon locked up as molecules of H20 inside or possbily just sticking to grains of lunar dust. 

Lunar Craters as imaged by NASA’s Moon Mineralogy Mapper. Image Credit: SRO/NASA/JPL-Caltech/USGS/Brown Univ.

The Chinese team are hunting down water ice in the south pole region where the low height of the Sun above the horizon means the heat arriving at the surface is less intense and doesn’t reach the bottom of the deep craters. It is in these cold regions they hope to find the ice and other volatile substances. 

They are not just hunting water though, they plan to explore the composition and shape or morphology of the lunar surface, the internal structure of the Moon, its magnetic fields and the general environment around the south pole. An intriguing element of the mission is the Lunar-Earth Very-Long baseline interferometry experiment which is exploring the viability of an interferometer with elements based on the Earth and on the Moon to give unprecedented resolution data.

In total, and to address all of these mission objectives, Change’e-7 will be home to a total of 18 payloads. The probe will consist of an orbiter, a lander, a rover and if that wasn’t enough, a miniature flying probe. If all goes to plan the lander will touchdown on the rim of a crater illuminated in sunlight near the south pole along with the rover and flying probe.  The probe will be armed to its teeth with instruments including; cameras, radar, water and minieral analyzers, spectrometers, magnetometers, seismograph and a volatiles detector. 

It is an ambious mission, chiefly due to the amount of technology and mission objectives but if it does all go well then Chang’e-7 will help us to learn more about the south pole of the Moon and also help to pave the way for a future long term lunar research station.

Source : China reveals goals, payloads of its lunar water-ice probe mission

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Venus is only slightly smaller than the Earth, and so has enjoyed billions of years of a warm heart. But for this planet, sometimes called Earth’s sister, that heat has betrayed it. That planet is now wrapped in suffocating layers of a poisonous atmosphere made of carbon dioxide and sulfuric acid. The pressures on the surface reach almost 100 times the air pressure at Earth’s sea level. The average temperatures are over 700 degrees Fahrenheit, more than hot enough to melt lead, while the deepest valleys see records of over 900 degrees.

If Venus is indeed Earth’s sister, she’s a twisted one. Like Mars, we suspect that Venus also once hosted a thinner, balmier atmosphere and a surface replete with liquid water oceans. The reasoning here is a little more tenuous than for Mars – where we can literally see the evidence for water before our very eyes – but the thinking is that both Venus and Earth formed in a roughly similar fashion, in roughly the same orbits with roughly the same material. Thus we should have been born with roughly the same amount of water.

Like Earth, most of that water would have been chemically bound up in rock, buried deep in the mantle. But some of it may have leeched to the surface or been delivered by hosts of water-rich comets shortly after formation, building up a supply on the surface, once again stabilized by a thick atmosphere.

What doomed Venus was not any fault of its own, but our own treacherous Sun. As stars age they gradually brighten. Day by day it’s imperceptible, but over the course of millions of years it completely changes the character of a star. Billions of years ago our Sun’s habitable zone was shifted inwards compared to where it rests now, but with increased brightness comes increased heat, and  that habitable zone steadily creeps outwards over time.

Did Venus ever host life? I doubt we’ll ever know, given the excruciating temperatures on the surface that make exploration nearly impossible. But it’s likely that it had water and a rich atmosphere – the basic ingredients were there. But if life did gain a foothold it did not last long. As our Sun aged, Venus got warmer and warmer. On a warmer planet, more water exists as vapor in the atmosphere than as liquid on the surface.

At first the changes were small, with nothing more than a higher dew point to mark the inexorable path to destruction. But at some point in the past – we are not sure exactly when – Venus reached a tipping point. With too much water vapor, the atmosphere of Venus became too good at trapping the heat radiating from the surface. That radiation could not penetrate the haze and make into space, but instead was ensnared within the atmosphere itself, heating it up.

What came next was, at least, mercifully quick. Venus entered a feedback loop, dumping more heat into the atmosphere, which boiled the oceans into more vapor, which increased the temperatures, and so on. First the shallow lakes and streams were gone, then came the deeper oceans, until every scrap of water was blowing in the winds of the atmosphere.

With its proximity to the ever-brightening Sun, the water vapor did not last long. Solar radiation pummeled it, disassociating its chemical bonds and sending the oxygen and hydrogen flying away, joining a grim procession beyond our solar system.

If Venus had plate tectonics like the Earth, then this is where that process came to end. With no water to act a lubricant, the great slow grinding of the plates seized up, locking the crust in place. This constant churning acts as a natural sink for carbon: the carbon dioxide binds to rocks which get pulled deep into the mantle, preventing too much carbon from building up in the atmosphere.

But without the cleansing effect of plate tectonics, carbon dioxide levels rose to dangerous heights, its own ability to absorb radiation from the surface choking off any remaining hope for rescuing the planet. Eventually the atmosphere would pile upon itself until it reached its present swollen size.

As our Sun aged, Venus strangled itself.

Venus is not alone in sharing that fate, for the Sun has not yet reached its final days. It continues to brighten, bringing more warmth to the solar system day by day, its habitable zone steadily inching outwards with every passing year.

At some point, approximately 500 million years from now, Venus will not be alone, The Earth’s oceans will boil, our continents will halt their ancient motion, and we will finally be twins with our sister: dead, lifeless, and strangling on our own bloated atmosphere.

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