Water on Ancient Mars?

 We all need a break from political news, so here's a cool story, slightly condensed, from Universe Today on the presence of water on ancient Mars.

There was Hot Water on Mars 4.45 Billion Years Ago

Earth and Mars were very similar in their youth. Four billion years ago, both planets had vast, warm seas. But while Earth retained its oceans, the waters of Mars evaporated away or froze beneath its dusty surface. Based on geological studies, we know that Earth’s water cycle seemed to have stabilized early. From about 4.5 billion years ago to today, water has had a stable presence on Earth. For Mars, things are less clear. Clay minerals cover about 45% of the Martian surface and date to what is known as the Noachian period, which ranges from 4.1 to 3.7 billion years ago. During the Amazonian period, which dates from 3 billion years ago to today, Mars seems to have been mostly dry. We have little evidence of the earliest period of Mars, known as the pre-Noachian. But a new study peels back the Martian ages to give us a glimpse of the first epoch of Mars, and it comes from a Martian meteorite known as Black Beauty.

This new study doesn’t focus on Black Beauty as a whole, but rather on small crystals of zircon embedded within it. These crystals can be dated to 4.48–4.43 billion years, meaning they formed in the Pre-Noachian period. What’s interesting is that the crystals have layers of iron, aluminum, and sodium in a pattern known as oscillatory zoning. Since zircon is igneous in origin, this kind of banding is almost unheard of in zircon crystals. On Earth, there is only one place where such a pattern occurs, which is in hydrothermal geysers such as those found in Yellowstone National Park.

The presence of these crystals in Black Beauty proves not only that Mars was wet during the Pre-Noachian period, but that it was geologically active with warm thermal vents. Similar vents on Earth may have triggered the formation of life on our world. Whether life ever existed on Mars is still an unanswered question, but it is clear that the conditions for life on Mars did exist in its earliest history.

Reference: Gillespie, Jack, et al. “Zircon trace element evidence for early hydrothermal activity on Mars.” Science Advances 110.47 (2024)

The Green Skies of Mars and Other Astronomical Wonders

Astronauts on Mars may see a green sky, eerie new study suggests

Using the European Space Agency's (ESA) ExoMars Trace Gas Orbiter (TGO), scientists have observed Mars' atmosphere glowing green for the first time ever — in the visible light spectrum, that is. The effect is called airglow (or dayglow or nightglow, depending on the hour). Nightglow "occurs when two oxygen atoms combine to form an oxygen molecule," according to ESA. On Mars, this happens at an altitude of approximately 31 miles (50 km). Scientists have suspected Mars to have airglow for some 40 years, but the first observation only occurred a decade ago by ESA's Mars Express orbiter, which detected the phenomenon in the infrared spectrum. Then, in 2020, scientists observed the phenomenon in visible light using TGO, but in Martian daylight rather than at night. Now, we've seen the phenomenon at night via TGO.

Moon is 40 million years older than we thought, tiny crystals from Apollo mission confirm

The moon is at least 40 million years older than we once thought, a new study reveals. Scientists confirmed our cosmic companion's new minimum age after reanalyzing tiny impact crystals from lunar samples taken by NASA's Apollo 17 mission in 1972. Earth is approximately 4.54 billion years old. So based on the newest study, the zircon crystals were formed around 80 million years after our planet formed. However, the collision that birthed the moon could have actually happened even earlier. After the Earth-Thea crash, the infant moon's surface would have been covered by a magma ocean due to the intense energy of the collision. Therefore, the lunar zircon crystals could only have properly solidified into their current state once the magma ocean had cooled down.

The oldest continents in the Milky Way may be 5 billion years older than Earth's

Astrobiologists think a planet needs to have certain features to support life: oxygen in its atmosphere, something to shield organisms from dangerous radiation and liquid water, for a start. Although big land masses aren't strictly necessary for living things to emerge, Earth's history shows that they're important for life to thrive and exist for long periods of time. So, if an exoplanet had continents before Earth, it follows that there might be older, more advanced life on that world.

This line of thought led Jane Greaves, an astronomer at Cardiff University astronomer in the U.K., to answer the question: When did the first continents appear on a planet in our galaxy? Turns out, two exoplanets' continents — and perhaps life — may have arisen four to five billion years before Earth's.

Can a Dead Star Keep Exploding?

If the Tasmanian Devil is a type of dead star, it’s not behaving like the others. As a dead star, the light coming from it could signal its transition into a sort of stellar afterlife. It could be a new type of stellar corpse.
“Because the corpse is not just sitting there, it’s active and doing things that we can detect,” Ho said. “We think these flares could be coming from one of these newly formed corpses, which gives us a way to study their properties when they’ve just been formed.”

The Echoes From Inflation Could Still Be Shaking the Cosmos Today

In the very early universe, physics was weird. A process known as “inflation,” where best we understand the universe went from a single infinitesimal point to everything we see today, was one such instance of that weird physics. Now, scientists from the Chinese Academy of Science have sifted through 15 years of pulsar timing data in order to put some constraints on what that physics looks like.

Life Might Be Easiest to Find on Planets that Match an Earlier Earth

When methane (CH4) and oxygen (O2) are both present in an atmosphere, it’s an indication that life is at work. That’s because, in an oxygen environment, methane only lasts about 10 years. Its presence indicates disequilibrium. For it to be present, it has to be continually replenished in amounts that only life can produce.

Planets and Nebulae and Stars, Oh My!

An embarrassment of riches of science articles:

Want to Find Life? Compare a Planet to its Neighbors

With thousands of known exoplanets and tens of thousands likely to be discovered in the coming decades, it could be only a matter of time before we discover a planet with life. The trick is proving it. So far the focus has been on observing the atmospheric composition of exoplanets, looking for molecular biosignatures that would indicate the presence of life. But this can be difficult since many of the molecules produced by life on Earth could also be produced by geologic processes. A new study argues that a better approach would be to compare the atmospheric composition of a potentially habitable world with those of other planets in the star system.

Since planets form within the debris disk of a young star, they will generally have similar compositions. Because of the migration of certain molecules such as water ice, the outer planets can have a slightly different composition than the inner planets, but overall their composition is similar. For this study, the team looked at the abundance of atmospheric carbon among worlds.

Carbon is not just a primary element for life on Earth, it also absorbs readily in water and can be bound geologically in rocks. So the idea is that if an exoplanet is in the potentially habitable zone of a star and has significantly less atmospheric carbon than similar worlds in its system, then that is a strong indicator of the presence of water and organic life. Take our solar system as an example. Earth, Venus, and Mars are all roughly in the habitable zone of the Sun, but both Venus and Mars have atmospheres comprised mostly of carbon dioxide. In contrast, Earth has an atmosphere of mostly nitrogen and oxygen, and only a fraction of a percent of carbon dioxide. Earth’s atmospheric carbon is so dramatically different from that of Venus and Mars that it stands out as a likely inhabited world.

The Crab Reveals Its Secrets To JWST

The Crab Nebula – otherwise known as the first object on Charles Messier’s list of non-cometary objects or M1 for short

It has been known that there is a pulsar at the core of the nebula, and it’s this pulsar that is the true remains of the progenitor star.  When it went ‘supernova,’ the core collapsed to form the ultra-dense rotating object that, if you happen to be in the right place in space (hey, that rhymes), then you will see a pulse of radiation as it rotates. The infrared images from JWST reveal synchrotron emissions, which are a direct result of the rapidly rotating pulsar.  As the pulsar rotates, the magnetic field accelerates particles in the nebula to astonishingly high speeds such that they emit synchrotron radiation. As a fabulously lucky quirk of nature, the radiation is particularly obvious in infrared, making it ideal for JWST. 

Uranus Has Infrared Auroras, Too

Auroras happen when charged particles in the solar wind and near-planet environment get trapped by a planet’s magnetic field. They funnel down to the atmosphere and collide with gas molecules. This happens on Earth and we see auroras over the north and south poles of our planet. They also happen at other planets. Astronomers detect them on the other giant planets, and a smaller version of them occurs on Mars. Venus probably doesn’t experience similar types of auroral displays, since it has no intrinsic magnetic field. However, it may experience something like them during particularly gusty solar wind events. At the outer planets, the gas mix is different in the atmospheres. That means their aurorae show up in ultraviolet and infrared wavelengths.

Uranus has an interesting magnetic field. It does not originate from the exact center of the planet. It’s also offset by 59 degrees from the rotation axis. That’s tipped 90 degrees from the plane of the solar system. This arrangement means that the Uranian magnetosphere is asymmetric and its field strengths vary depending on location. It connects with the solar wind once every Uranian day (which is 17 hours long). The planet does show some auroral activity, particularly around the poles and Hubble Space Telescope detected some in 2011

Three Planets Around this Sunlike Star are Doomed. Doomed!

According to new research we can start writing the eulogy for four exoplanets around a Sun-like star about 57 light years away. But there’s no hurry; we have about one billion years before the star becomes a red giant and starts to destroy them.

The star is Rho Coronae Borealis, a yellow dwarf star like our Sun. It’s in the constellation Corona Borealis, and has almost the same mass, radius, and luminosity as the Sun. The difference is in their ages. The Sun is about five billion years old, but Rho CrB is twice that, which means its red giant phase is imminent, at least in astrophysical terms.

Post main sequence stellar evolution can result in dramatic, and occasionally traumatic, alterations to the planetary system architecture, such as tidal disruption of planets and engulfment by the host star,” Kane writes. Rho Coronae Borealis is both old and bright, making it “… a particularly interesting case of advanced main sequence evolution,” according to Kane. Not only because its similar to the Sun and easily observed, but also because it hosts four exoplanets.

White Dwarfs Could Support Life. So Where are All Their Planets?

Astronomers have found plenty of white dwarf stars surrounded by debris disks. Those disks are the remains of planets destroyed by the star as it evolved. But they’ve found one intact Jupiter-mass planet orbiting a white dwarf.

Are there more white dwarf planets? Can terrestrial, Earth-like planets exist around white dwarfs?

A white dwarf (WD) is the stellar remnant of a once much-larger main sequence star like our Sun. When a star in the same mass range as our Sun leaves the main sequence, it swells up and becomes a red giant. As the red giant ages and runs out of nuclear fuel, it sheds its outer layers as a planetary nebula, a shimmering veil of expanding ionized gas that everybody’s seen in Hubble images. After about 10,000 years, the planetary nebula dissipates, and all that’s left is a white dwarf, alone in the center of all that disappearing glory.

White dwarfs are extremely dense and massive, but only about as large as Earth. They’ve left their life of fusion behind, and emit only residual heat. But still, heat is heat, and white dwarfs can have habitable zones, though they’re very close.

Astronomers are pretty certain that most stars have planets. But those planets are in peril when they orbit a star that leaves the main sequence behind and becomes a red giant. That can wreak havoc on planets, consuming some of them and tearing others apart by tidal disruption. Some white dwarfs are surrounded by debris disks, and they can only be the remains of the star’s planets, ripped to pieces by the star during its red dwarf stage.

But in 2020 researchers announced the discovery of an intact planet among the debris disk in the habitable zone around the white dwarf WD1054-226. If there’s one, there are almost certainly others out there somewhere. Why haven’t we found them? And does the fact that the first one we’ve found is a Jupiter-mass planet mean the WD exoplanet population is dominated by them?

Old Data from Kepler Turns Up A System with Seven Planets

NASA’s Kepler mission ended in 2018 after more than nine years of fruitful planet-hunting. The space telescope discovered thousands of planets, many of which bear its name. But it also generated an enormous amount of data that exoplanet scientists are still analyzing.

Kepler 385 is similar to the Sun but a little larger and hotter. It’s 10% larger and about 5% hotter. It’s one of a very small number of stars with more than six planets or planet candidates orbiting it.

The two innermost planets are both slightly larger than Earth. According to the new catalogue, they’re both probably rocky. They may even have atmospheres, though if they do, they’re very thin. The remaining five planets have radii about twice as large as Earth’s and likely have thick atmospheres.

Trojan Planets, Diamond Stars, and Other Astronomical Wonders

1st known 'Trojan' planets discovered locked in the exact same orbit around a star

Astronomers have discovered the first evidence of ultra-rare 'Trojan' planets: two sibling planets bound on the same orbit around the same star.

The potential co-orbiting planets, dancing around the young star PDS 70 roughly 370 light-years away, consist of a Jupiter-size planet and a cloud of debris — possibly the shattered remains of a dead planet, or the gathering building blocks of one yet to be born.

 
Trojan planets get their unusual name from the two asteroid clusters seen around Jupiter, which, upon their discovery, were split into Greeks and Trojans (the opposing sides of the mythical Trojan War in Homer's Iliad) based on their proximity to the gas giant's gravitationally stable Lagrange points.

Lagrange points are places in a solar system where the gravitational pulls of a star and an orbiting planet balance out the motion of an object's orbit, trapping the object so that it moves in lock-step with the planet.

A White Dwarf is Starting to Crystallize into Diamond

White dwarfs are truly strange objects. After a lifetime of billions of years of fusion, they transform themselves into something else completely different. They transition from blazing balls of plasma to degenerate lumps of carbon that eventually crystallize into diamonds that last for unimaginably long time periods.

It takes a quadrillion years for a white dwarf to crystallize, and since the Universe is not even 14 billion years old, astronomers will never spot a fully crystallized one. But this research removes some of the mystery by finding one that’s just starting to become a cosmic diamond. Curious astronomers will study more of these bizarre stellar remnants, and one day, we may know exactly how and when something so strange can happen.

A skyscraper-size asteroid flew closer to Earth than the moon — and scientists didn't notice until 2 days later

Now dubbed 2023 NT1, the roughly 200-foot-wide (60 meters) space rock sailed past our planet on July 13, traveling at an estimated 53,000 mph (86,000 km/h), according to NASA. However, because the rock flew toward Earth from the direction of the sun, our star's glare blinded telescopes to the asteroid's approach until long after it had passed.

Astronomers didn't catch wind of the building-size rock until July 15, when a telescope in South Africa — part of the Asteroid Terrestrial-impact Last Alert System (ATLAS), an array of telescopes designed to spot asteroids several days to weeks before any potential impact — caught the rock making its exit from our neighborhood. More than a dozen other telescopes also spotted the rock shortly afterward, according to the International Astronomical Union's Minor Planet Center.

Hundreds of 'ghost stars' haunt the Milky Way's center. Scientists may finally know why

"Planetary nebulas offer us a window into the heart of our galaxy and this insight deepens our understanding of the dynamics and evolution of the Milky Way's bulge region," University of Manchester astrophysicist Albert Zijlstra said in a statement.

Studying 136 planetary nebulas in the thickest part of the Milky Way, the galactic bulge, with the Very Large Telescope (VLT), the team discovered that each is unrelated and comes from different stars, which died at different times and spent their lives in different locations.

The researchers also found that the shapes of these planetary nebulas line up in the sky in the same way. Not only this, but they are also aligned almost parallel to the plane of the Milky Way.

Let's Build a World: New Astronomical Finds for Your SF Stories

I've got a file (actually a dozen files) of cool science stories that I might use in science fictional world-building. What sf author doesn't? Even fantasy stories need good science. For instance, an urban fantasy involving werewolves really should depict the phases of the moon accurately. This week, images and data from the Hubble and James Webb Space Telescopes have furnished a treasure trove of research ideas. Rather than post them separately, I've gathered a few that I find particularly exciting.

There Could be Many Water Worlds in the Milky Way

Astronomers are curious about how many terrestrial planets in our galaxy are actually “water worlds.” 
These are rocky planets that are larger than Earth but have a lower density, which suggests that volatiles like water make up a significant amount (up to half) of their mass-fraction. According to a recent study by researchers from the University of Chicago and the Instituto de Astrofísica de Canarias (IAC), water worlds may be just as common as “Earth-like” rocky planets. These findings bolster the case for exoplanets that are similar to icy moons in the Solar System (like Europa) and could have significant implications for future exoplanet studies and the search for life in our Universe.

“We have discovered the first experimental proof that there is a population of water worlds, and that they are in fact almost as abundant as Earth-like planets. We found that it is the density of a planet and not its radius, as was previously thought, which separates dry planets from wet ones. The Earth is a dry planet, even though its surface is mostly covered in water, which gives it a very wet appearance. The water on Earth is only 0.02% of its total mass, while in these water worlds it is 50% of the mass of the planet.”

However, planets around M-type stars typically orbit so closely that they are tidally locked, where one side is constantly facing toward its sun. At this distance, any water on the planet’s surface would likely exist in a supercritical gas phase, increasing their sizes. As a result, Luque and Pallé theorized that in this population, water is bound to the rock or in closed volumes below the surface, not in the form of oceans, lakes, and rivers on the surface. These conditions are similar to what scientists have observed with icy moons in the outer Solar System, such as Jupiter’s moon Europa and Saturn’s moon Titan.

Given that they are tidally locked to their suns, these planets may also have liquid oceans on their sun-facing side but frozen surfaces everywhere else – colloquially known as “eyeball planets.” While astronomers have speculated about the existence of this class of exoplanet, these findings constitute the first confirmation for this new type of exoplanet. They also bolster the growing case for water worlds that form beyond the so-called “snow line” in star systems (the boundary beyond which volatile elements freeze solid), then migrate closer to their star.

In the past, glaciers may have existed on the surface of Mars, providing meltwater during the summer to create the features we see today. Credit: NASA/JPL-Caltech/ESA

Mars Had Moving Glaciers, but They Behaved Differently in the Planet's Lower Gravity

On Earth, shifts in our climate have caused glaciers to advance and recede throughout our geological history (known as glacial and inter-glacial periods). The movement of these glaciers has carved features on the surface, including U-shaped valleys, hanging valleys, and fjords. These features are missing on Mars, leading scientists to conclude that any glaciers on its surface in the distant past were stationary. However, new research by a team of U.S. and French planetary scientists suggests that Martian glaciers did move more slowly than those on Earth.

These findings demonstrate how glacial ice on Mars would drain meltwater much more efficiently than glaciers on Earth. This would largely prevent lubrication at the base of the ice sheets, which would lead to faster sliding rates and enhanced glacial-driven erosion. In short, their study demonstrated that lineated landforms on Earth associated with glacial activity would not have had time to develop on Mars.

In addition to explaining why Mars lacks certain glacial features, the work also has implications for the possibility of life on Mars and whether that life could survive the transition to a global cryosphere we see today. According to the authors, an ice sheet could provide a steady water supply, protection, and stability to any subglacial bodies of water where life could have emerged. They would also protect against solar and cosmic radiation (in the absence of a magnetic field) and insulation against extreme variations in temperature.

White Dwarf Stars and Other Wonders

White dwarf’s inner makeup is mapped for the first time

Tiny changes in a white dwarf’s brightness reveal that the stellar corpse has more oxygen in its core than expected, researchers report online January 8 in Nature. The finding could challenge theories of how stars live and die, and may have implications for measuring the expansion of the universe.

As a star ages, it sheds most of its gas into space until all that remains is a dense core of carbon and oxygen, the ashes of a lifetime of burning helium. That core, plus a thin shellacking of helium, is called a white dwarf.

Luckily, some white dwarfs encode their inner nature on their surface. These stars change their brightness in response to internal vibrations. Astrophysicists can infer a star’s internal structure from the vibrations, similar to how geologists learn about Earth’s interior by measuring seismic waves during an earthquake.

Saturn’s rings, made of countless icy particles, form a translucent veil in this view from NASA’s Cassini spacecraft.

Saturn's moon Titan sports Earth-like features

Using the now-complete Cassini data set, Cornell astronomers have created a new global topographic map of Saturn's moon Titan that has opened new windows into understanding its liquid flows and terrain.

The map revealed several new features on Titan, including new mountains, none higher than 700 meters. The map also provides a global view of the highs and lows of Titan's topography, which enabled the scientists to confirm that two locations in the equatorial region of Titan are in fact depressions that could be either ancient, dried seas or cryovolcanic flows.

The map also revealed that Titan is a little bit flatter -- more oblate -- than was previously known, which suggests there is more variability in the thickness of Titan's crust than previously thought.

Extrasolar Planets

Stars orbit the center of mass of their systems (not center of star mass); hence, planets can perturb a star's orbit. Stars wobble due to tiny gravitational effects of their planets (meters per second). Look for shifts in the absorption spectra; from the period and size of the shift, we can determine the mass of an object affecting a star. A star's motion can be influenced by multiple planets, but it is still possible to determine their masses and orbits. Detecting these very tiny shifts requires precision technology.

Astrometric technique; we can detect planets by measuring changes in star's position.

Doppler shifts detected in the spectroscopic analysis of 51 Pegasi indirectly revealed a planet with 4 day orbit (50 m/sec). Rapid period means the orbit is small and the planet is close to the star. Discovered 1995. Mass similar to Jupiter but within radius of Mercury. This class of planets are called "hot Jupiters."

Launch Pad Diary: Very Cool Stuff About Planets

Planets are teeny specks in the middle of nothing, separated by vast distances. 8 major planets with nearly circular orbits; Pluto and Eris are smaller and have more elliptical orbits; Pluto-like objects (many!) Eris is larger than Pluto! (Kuiper belt, objects rocky and icy like comets, 1/2 dozen we know about so far.)

Sun comprises 99.9% of solar system's mass, mostly H/He gas; converts 4 million tons of mass into energy each second.

Mercury - metal and rock, large iron core; desolate, cratered with long, tall steep cliffs, very hot/cold 425oC to -170oC Why iron core: During planetary accretion, lighter elements blown off, only heavier elements left. Outer planets - ices solid, grow bigger and more quickly than inner planets. Jupiter orbit = "frost line" for volatile gases being ice (but we are having to re-think the frost line in light of "hot Jupiters" that orbit very close to their stars.)