Cassini Sees Earth and Moon Through Saturn’s Rings

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NASA/JPL-Caltech/Space Science Institute

NASA’s Cassini mission sure has a knack for putting stuff into perspective — and this most recent view from Saturn orbit is no different. That dot in the center of the image isn’t a dud pixel in Cassini’s camera CCD. That’s us. All of us. Everyone.

To quote Carl Sagan:

“Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives…”

Sagan wrote that passage in his book “Pale Blue Dot: A Vision of the Human Future in Space” when reflecting on the famous “Pale Blue Dot” image that was beamed back to Earth by NASA’s Voyager 1 spacecraft in 1990. That’s when the mission returned a profound view of our planet from a distance of 3.7 billion miles (or 40.5AU) as it was traveling through the solar system’s hinterlands, on its way to interstellar space. Since then, there’s been many versions of pale blue dots snapped by the armada of robotic missions around the solar system and Cassini has looked back at us on several occasions from its orbital perch.

Now, just before Cassini begins the final leg of its Saturnian odyssey, it has again spied Earth through a gap between the gas giant’s A ring (top) and F ring (bottom). In a cropped and enhanced version, our moon is even visible! The image is composed of many observations captured on April 12, stitched together as a mosaic when Saturn was 870 million miles (roughly 9.4AU) from Earth.

On April 20 (Friday), Cassini will make its final flyby of Titan, Saturn’s largest moon, using its gravity to fling itself through Saturn’s ring plane (on April 26) between the innermost ring and the planet’s cloudy upper atmosphere, revealing a view that we’ve never before seen. For 22 orbits, Cassini will dive into this uncharted region, possibly revealing new things about Saturn’s evolution, what material its rings contain and incredibly intimate views of its atmosphere.

This daring maneuver will signal the beginning of the end for this historic mission, however. On Sept. 15, Cassini will be intentionally steered into Saturn’s atmosphere to burn up as a human-made meteor. It is low in fuel, so NASA wants to avoid the spacecraft from crashing into and contaminating one of Saturn’s potentially life-giving moons — Titan or Enceladus.

So, appreciate every image that is captured by Cassini over the coming weeks. The pictures will be like nothing we’ve seen before of the ringed gas giant, creating a very bittersweet phase of the spacecraft’s profound mission to Saturn.

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Enceladus Could Be a Cosmic Shaker for the Cocktail of Life

NASA/JPL-Caltech/Space Science Institute

A little frozen Saturn moon, with a diameter that could easily fit inside the state of New Mexico, holds some big promises for the possibility of finding basic alien life in our solar system.

Enceladus is often overshadowed by its larger distant cousin, Europa, which orbits Jupiter and the Jovian moon’s awesome potential has been widely publicized. But Enceladus has one thing Europa doesn’t — it has been visited very closely by a robotic space probe that could take a sniff of its famous water vapor plumes. And this week, there was much excitement about another facet of the moon’s complex subsurface chemistry, thanks to analysis carried out on data gathered by NASA’s Cassini mission.

But before we get into why this new discovery is so cool, let’s take a very quick look at the other signs of Enceladus’ life-giving potential.

The Cocktail Of Life

Being living, breathing creatures on a habitable planet, it may not come as a surprise to you that for biology to evolve, it needs a few basic ingredients. Liquid water is a definite requirement, of course. Heat also helps. Throw some organic chemistry into the mix and we have a party.

Enceladus, however, is a tiny icy globe, there’s no sign of liquid water on its surface. But when Cassini arrived at Saturn in 2004, Enceladus revealed some of its best-kept secrets. Firstly, it may be a smooth ice ball, but the moon has a large quantity of water under its surface. This water even escapes as geysers, through fissures in its icy crust, producing stunning plumes that eject material hundreds of miles high and into Saturn’s rings.

Before Cassini was launched to Saturn, we had little clue about Enceladus’ watery potential — though this finding explained why Enceladus appeared so bright and how it contributes material to Saturn’s E-ring. Fortunately, the spacecraft has an instrument on board — a mass spectrometer — that could be used to “taste” the watery goodness of these plumes. During its Enceladus flybys, Cassini was able to fly through the plumes, revealing a surprisingly rich chemical cocktail — including a high concentration of organic chemistry.

It’s as if all the building blocks of life have been thrown into a small icy cocoon, shaken up and gently heated from within.

Now, another fascinating discovery has been made. Further analysis of Cassini data from its last 2015 plume fly-through, molecular hydrogen has been detected and planetary scientists are more than a little excited to add this to Enceladus’ habitable repertoire.

Deep In The Enceladus Abyss

“Hydrogen is a source of chemical energy for microbes that live in the Earth’s oceans near hydrothermal vents,” said Hunter Waite, principal investigator of Cassini’s Ion Neutral Mass Spectrometer (INMS) at the Southwest Research Institute (SwRI), in a statement on Thursday (April 13). “Our results indicate the same chemical energy source is present in the ocean of Enceladus.”

This hydrogen could be a byproduct of chemical reactions going on between the moon’s rocky core and the warm water surrounding it. And there’s a lot of hydrogen gas being vented, probably enough to sustain basic lifeforms deep in the Enceladus abyss.

“The amount of molecular hydrogen we detected is high enough to support microbes similar to those that live near hydrothermal vents on Earth,” added co-author Christopher Glein, who specializes in extraterrestrial chemical oceanography, also of SwRI. “If similar organisms are present in Enceladus, they could ‘burn’ the hydrogen to obtain energy for chemosynthesis, which could conceivably serve as a foundation for a larger ecosystem.”

Yes, we’re talking alien microbes. (Also, “extraterrestrial chemical oceanography” — oceans on other worlds! — is one hell of a mind-blowing topic to specialize in, just sayin’.) And did he mention “larger ecosystem”? Why yes! Yes he did.

So, in short, we know Enceladus has a liquid water ocean. We know that it has an internal heat source (hence the liquid oceans). We also know there’s organic chemistry. And now there’s solid hints that there’s water-rock interactions going on that terrestrial microbes living at Earth’s ocean vents like to munch on. If that’s not a huge, blinking neon sign pointing at Enceladus, saying: “We need a surface mission here!” I don’t know what is.

Although the researchers are keen to emphasize that alien microbes have not been found (because Cassini isn’t capable of looking for life), the universe has given us a moon-sized Petri dish where an “ecosystem” may have taken hold. All the ingredients are there, wouldn’t it be cool to find out if Enceladus could be another place in the solar system where life may be hanging out?

There was also some great news about Europa’s habitable potential this week, but you can go here for that piece of cosmic awesomeness.

Want to know more about Cassini’s final months at Saturn, check out my recent Space.com article on the commencement of the veteran mission’s Grand Finale.

Smallest ‘Super-Earth’ Discovered With an Atmosphere — but It’s No Oasis

MPIA

For the first time, astronomers have detected an atmosphere around a small (and likely) rocky exoplanet orbiting a star only 39 light-years away. Although atmospheres have been detected on larger alien worlds, this is the smallest world to date that has been found sporting atmospheric gases.

Alas, Gliese (GJ) 1132b isn’t a place we’d necessarily call “habitable”; it orbits its red dwarf a little too close to have an atmosphere anything like Earth’s, so you’d have to be very optimistic if you expect to find life (as we know it) camping there. But this is still a huge discovery that is creating a lot of excitement — especially as this exo-atmosphere has apparently evolved intact so close to a star.

The atmosphere was discovered by an international team of astronomers using the 2.2 meter ESO/MPG telescope at La Silla Observatory in Chile. As the exoplanet orbited in front of the star from our perspective (known as a “transit”), the researchers were able to deduce the physical size of the world by the fraction of starlight it blocked. The exoplanet is around 40 percent bigger than Earth (and 60 percent more massive) making it a so-called “super-Earth.”

Through precision observations of the infrared light coming from the exoplanet during the 1.6 day transits, the astronomers noticed that the planet looked larger at certain wavelengths of light than others. In short, this means that the planet has an atmosphere that blocks certain infrared wavelengths, but allows other wavelengths to pass straight through. Researchers of the University of Cambridge and the Max Planck Institute for Astronomy then used this information to model certain chemical compositions, leading to the conclusion that the atmosphere could be a thick with methane or water vapor.

Judging by the exoplanet’s close proximity to its star, this could mean that the planet is a water world, with an extremely dense and steamy atmosphere. But this is just one of the possibilities.

“The presence of the atmosphere is a reason for cautious optimism,” writes a Max Planck Institute for Astronomy news release. “M dwarfs are the most common types of star, and show high levels of activity; for some set-ups, this activity (in the shape of flares and particle streams) can be expected to blow away nearby planets’ atmospheres. GJ 1132b provides a hopeful counterexample of an atmosphere that has endured for billion of years (that is, long enough for us to detect it). Given the great number of M dwarf stars, such atmospheres could mean that the preconditions for life are quite common in the universe.”

To definitively work out what chemicals are in GJ 1132b’s atmosphere, we may not be waiting that long. New techniques for deriving high-resolution spectra of exoplanetary atmospheres are in the works and this exoplanet will be high on the list of priorities in the hunt for extraterrestrial biosignatures. (For more on this, you can check out a recent article I wrote for HowStuffWorks.)

Although we’ll not be taking a vacation to GJ 1132b any time soon, the discovery of an atmosphere around such a small alien world will boost hopes that similar sized super-Earths will also host atmospheres, despite living close to red dwarf stars that are known for their flaring activity. If atmospheres can persist, particularly on exoplanets orbiting within a star’s so-called habitable zone, then there really should be cause for optimism that there really might be an “Earth 2.0” out there orbiting one of the many red dwarfs in our galaxy.

Mars Rover Curiosity’s Wheels Are Taking a Battering

The NASA robot continues to rove the unforgiving slopes of Mount Sharp, but dramatic signs of damage are appearing on its aluminum wheels.

NASA/JPL-Caltech/MSSS

In 2013, earlier than expected signs of damage to Curiosity’s wheels were causing concern. Four years on and, unsurprisingly, the damage has gotten worse. The visible signs of damage have now gone beyond superficial scratches, holes and splits — on Curiosity’s middle-left wheel (pictured above), there are two breaks in the raised zigzag tread, known as “grousers.” Although this was to be expected, it’s not great news.

The damage, which mission managers think occurred some time after the last wheel check on Jan. 27, “is the first sign that the left middle wheel is nearing a wheel-wear milestone,” said Curiosity Project Manager Jim Erickson, at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., in a statement.

After the 2013 realization that Curiosity’s aluminum wheels were accumulating wear and tear faster than hoped, tests on Earth were carried out to understand when the wheels would start to fail. To limit the damage, new driving strategies were developed, including using observations from orbiting spacecraft to help rover drivers chart smoother routes.

It was determined that once a wheel suffers three grouser breaks, the wheel would have reached 60 percent of its useful life. Evidently, the middle left wheel is almost there. According to NASA, Curiosity is still on course for fulfilling its science goals regardless of the current levels of wheel damage.

“This is an expected part of the life cycle of the wheels and at this point does not change our current science plans or diminish our chances of studying key transitions in mineralogy higher on Mount Sharp,” added Ashwin Vasavada, Curiosity’s Project Scientist also at JPL.

While this may be the case, it’s a bit of a downer if you were hoping to see Curiosity continue to explore Mars many years beyond its primary mission objectives. Previous rover missions, after all, have set the bar very high — NASA’s Mars Exploration Rover Opportunity continues to explore Meridiani Planum over 13 years since landing in January 2004! But Curiosity is a very different mission; it’s bigger, more complex and exploring a harsher terrain, all presenting very different engineering challenges.

Currently, the six-wheeled rover is studying dunes at the Murray formation and will continue to drive up Mount Sharp to its next science destination — the hematite-containing “Vera Rubin Ridge.” After that, it will explore a “clay-containing geological unit above that ridge, and a sulfate-containing unit above the clay unit,” writes NASA.

Since landing on Mars in August 2012, the rover has accomplished an incredible array of science, adding amazing depth to our understanding of the Red Planet’s habitable potential. To do this, it has driven 9.9 miles (16 kilometers) — and she’s not done yet, not by a long shot.

Mars May Have Once Been a Ringed Planet — and It Could Be Again

Mars’ moons were likely formed by a ring of debris blasted into space after the Red Planet was hit by a massive impact and, when the moon Phobos disintegrates in 70 million years, another ring may form.

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Sunrise over Gale Crater as seen by NASA’s Mars rover Curiosity and how it might look if the Red Planet had a ring system (NASA/JPL-Caltech-MSSS, edit by Ian O’Neill)

Mars is currently known as the “Red Planet” of the solar system; its unmistakable ruddy hue is created by dust rich in iron oxide covering its landscape. But in Mars’ ancient past, it might have also been called the “Ringed Planet” of the inner solar system and, in the distant future, it may sport rings once more.

The thing is, we live in a highly dynamic solar system, where the planets may appear static over human (or even civilization) timescales, but over millions to billions of years, massive changes to planetary bodies occur frequently. And should there be a massive impact on a small rocky world — on Mars, say — these changes can be nothing short of monumental.

In new NASA-funded research published in the journal Nature Geoscience, planetary scientists have developed a new model of Mars when it was hit by a massive impact over 4 billion years ago. This catastrophic impact created a vast basin called the Borealis Basin in the planet’s northern hemisphere and the event could be part of the reason why Mars lacks a global magnetic field — it’s hypothesized that a powerful impact (or series of impacts) caused massive disruption to the Martian inner dynamo.

But the impact also blasted a huge amount of rocky debris from Mars’ crust into space, ultimately settling into a ring system, like a miniaturized rocky version of Saturn. Over time, as the debris drifted away from Mars and settled, rocky chunks would have formed under gravity and these “moonlets” would have clumped together to form larger and larger moons. So far, so good; this is how we’d expect moons to form. But there’s a catch.

Phobos as imaged by Europe’s Mars Express mission (ESA)

After forming in Mars orbit, any moon would have slowly lost orbital altitude, creeping toward the planet’s so-called Roche Limit — a region surrounding any planetary body that is a bad place for any moon to hang out. The Roche Limit is the point at which a planet’s tidal forces become too great for the structural integrity of an orbiting body. When approaching this limit, the closest edge of the moon to the planet will experience a greater tidal pull than the far side, overcoming the body’s gravity. At some point, something has to give and the moon will start to break apart.

And this is what’s going to happen to Phobos in about 70 million years. Its orbit is currently degrading and when it reaches this invisible boundary, tidal stresses will pull it apart, trailing pieces of moon around the planet, some debris falling onto the Martian surface as a series of meteorite impacts, while others remain in orbit.

The research, carried out by David Minton and Andrew Hesselbrock of Purdue University, Lafayette in Indiana, theorizes that mysterious deposits of material around Mars’ equator might have come from the breakup of ancient moons that came before Phobos and Deimos.

“You could have had kilometer-thick piles of moon sediment raining down on Mars in the early parts of the planet’s history, and there are enigmatic sedimentary deposits on Mars with no explanation as to how they got there,” said Minton. “And now it’s possible to study that material.”

According to their model, each time a moon broke apart to create a ring, the next moon would be five times smaller than its predecessor.

In short, Mars and its moon may appear to be pretty much unchanged for billions of years, but the researchers think that up to seven moon-ring cycles have occurred over the last 4.3 billion years and Mars is on the verge (on geological timescales) of acquiring rings once more. Fascinating.

Mysterious Fomalhaut b Might Not Be an Exoplanet After All

The famous exoplanet was the first to be directly imaged by Hubble in 2008 but many mysteries surround its identity — so astronomers are testing the possibility that it might actually be an exotic neutron star.

NASA, ESA, P. Kalas, J. Graham, E. Chiang, E. Kite (University of California, Berkeley), M. Clampin (NASA Goddard Space Flight Center), M. Fitzgerald (Lawrence Livermore National Laboratory), and K. Stapelfeldt and J. Krist (NASA Jet Propulsion Laboratory)

Located 25 light-years from Earth, the bright star Fomalhaut is quite the celebrity. As part of a triple star system (its distant, yet gravitationally bound siblings are orange dwarf TW Piscis Austrini and M-type red dwarf LP 876-10) Fomalhaut is filled with an impressive field of debris, sharing a likeness with the Lord Of The Rings’Eye of Sauron.” And, in 2008, the eerie star system shot to fame as the host of the first ever directly-imaged exoplanet.

At the time, the Hubble Space Telescope spotted a mere speck in Fomalhaut’s “eye,” but in the years that followed the exoplanet was confirmed — it was a massive exoplanet approximately the size of Jupiter orbiting the star at a distance of around 100 AU (astronomical units, where 1 AU is the average distance the Earth orbits the sun). It was designated Fomalhaut b.

This was a big deal. Not only was it the first direct observation of a world orbiting another star, Hubble was the aging space telescope that found it. Although the exoplanet was confirmed in 2013 and the International Astronomical Union (IAU) officially named the exoplanet “Dagon” after a public vote in 2015, controversy surrounding the exoplanet was never far away, however.

Astronomers continue to pick at Fomalhaut’s mysteries and, in new research to be published in the journal Monthly Notices of the Royal Astronomical Society, Fomalhaut b’s identity has been thrown into doubt yet again.

“It has been hypothesized to be a planet, however there are issues with the observed colors of the object that do not fit planetary models,” the researchers write. “An alternative hypothesis is that the object is a neutron star in the near fore- or background of Fomalhaut’s disk.” The research team is lead by Katja Poppenhaeger, of Queen’s University, Belfast, and a preprint of their paper (“A Test of the Neutron Star Hypothesis for Fomalhaut b”) can be found via arXiv.org.

Artist’s impression of Fomalhaut b inside its star’s debris disk (ESA, NASA, and L. Calcada – ESO for STScI)

Fomalhaut b was detected in visible and near-infrared wavelengths, but followup studies in other wavelengths revealed some peculiarities. For starters, the object is very bright in blue wavelengths, something that doesn’t quite fit with exoplanetary formation models. To account for this, theorists pointed to a possible planetary accretion disk like a system of rings. This may be the reason for the blue excess; the debris is reflecting more starlight than would be expected to be reflected by the planet alone. However, when other studies revealed the object is orbiting outside the star system’s orbital plane, this explanation wasn’t fully consistent with what astronomers were seeing.

Other explanations were put forward — could it be a small, warm world with lots of planetesimals surrounding it? Or is it just a clump of loosely-bound material and not a planet at all? — but none seem to quite fit the bill.

In this new research, Poppenhaeger’s team pondered the idea that Fomalhaut b might actually be a neutron star either in front or behind the Fomalhaut debris disk and, although their work hasn’t proven whether Fomalhaut b is an exoplanet or not, they’ve managed to put some limits on the neutron star hypothesis.

Neutron stars are the left-overs of massive stars that have run out of fuel and gone supernova. They are exotic objects that are extremely dense and small and, from our perspective, may produce emissions in visible and infrared wavelengths that resemble a planetary body. Cool and old neutron stars will even generate bluer light, which could explain the strange Fomalhaut b spectra.

Neutron stars also produce ultraviolet light and X-rays and, although it is hard to separate the UV light coming from the exoplanet and the UV light coming from the star, X-ray emissions should be resolvable.

Artist’s impression of a magnetar, an extreme example of a neutron star (ESO/L.Calçada)

So, using observations from NASA’s Chandra X-ray Observatory, the researchers looked at Fomalhaut b in soft X-rays and were able to put some pretty strong constraints on whether or not this object really could be a neutron star. As it turned out, Chandra didn’t detect X-rays (within its capabilities). This doesn’t necessarily mean that it isn’t a neutron star, it constrains what kind of neutron star it could be. Interestingly, it also reveals how far away this object could be.

Assuming it is a neutron star with a typical radius of 10 kilometers, and as no X-ray emissions within Chandra’s wavelength range were detected, this object would be a neutron star with a surface temperature cooler than 90,000 Kelvin — revealing that it is over 10 million years old. For this hypothesis to hold, the neutron star would actually lie behind the Fomalhaut system, around 44 light-years (13.5 parsecs) from Earth.

Further studies are obviously needed and, although the researchers point out that Fomalhaut b is still most likely an exoplanet with an extensive ring system (just with some strange and as-yet unexplained characteristics), it’s interesting to think that it could also be a neutron star that isn’t actually in the Fomalhaut system at all. In fact, it could be the closest neutron star to Earth, providing a wonderful opportunity for astronomical studies of these strange and exotic objects.

Cassini Says “Ciao!” to Pan, Saturn’s Ravioli Moon

Never before has a space probe come so close to the pint-sized moon embedded in Saturn’s rings — and when NASA’s Cassini buzzed Pan, the spacecraft revealed what a strange moon it really is.

NASA/JPL-Caltech/Space Science Institute

This is Pan, a 22 mile-wide moon that scoots through Saturn’s rings, orbiting the gas giant once every 13.8 hours. And it’s weird.

Resembling a giant ravioli or some kind of “flying saucer” from a classic alien invasion sci-fi comic, Pan is known as a “shepherd moon” occupying the so-called Encke Gap inside Saturn’s A Ring. This gap is largely free of particles and it has become Pan’s job to hoover up any stray material — the moon’s slight gravity pulls particles onto its surface and scatters others back out into the ring system. This gravitational disturbance creates waves that ripple through the ring material, propagating for hundreds of miles.

On March 7, NASA’s Cassini mission came within 15,268 miles of Pan, revealing incredible detail in the moon’s strange surface. It’s thought that its characteristic equatorial ridge (a trait it shares with another Saturn moon Atlas) is caused by the gradual accumulation of ring material throughout the moon’s formation and with these new observations, scientists will be able to better understand how Pan came to be.

NASA/JPL-Caltech/Space Science Institute

As Cassini rapidly approaches the end of its mission, eventually orbiting through Saturn’s ring plane as a part of its “Grand Finale,” we can expect more of these striking views from orbit before the veteran probe is steered into Saturn’s atmosphere in September, bringing its historic mission to an end.

Can We Call the Bright Spot in Ceres’ Occator Crater a Cryovolcano Yet?

Evidence is mounting around the cryovolcanic history of the solar system’s innermost dwarf planet — and its most recent eruptions may have happened within the last four million years.

NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Since NASA’s Dawn mission arrived at dwarf planet Ceres in 2015, we’ve been treated to some wonderfully detailed images of the small world’s pockmarked terrain. Understanding the underlying processes of what is believed to be an ice-filled celestial body, however, is taking some time to decipher. But with more observations comes more understanding and planetary scientists are getting close to realizing what lies beneath those craters and, possibly, unlocking the secrets behind a very icy and very alien phenomenon we have no experience of in our terrestrial lives.

That phenomenon is cryovolcanoes. And Ceres seems to have them.

The most startling feature on Ceres is Occator Crater. This 57 mile-wide feature is the result of a massive impact tens of millions of years ago. Large craters on small worlds isn’t necessarily a strange thing in our battered solar system, but what is strange about Occator is the very bright feature (and small bright patches surrounding it) in the crater’s center. Even before Dawn arrived in orbit and only fuzzy images of Ceres were available, hopes were high that this bright anomaly in the otherwise gray Cererian landscape could be indicative of ices or some mineral compound that was formed by the presence of water.

There have been many studies into Occator’s icy center, but new research into the crater’s age compared to the bright spot’s age appears to, once again, point to a cryovolcanic origin.

Cryovolcanoes — or, simply, ice volcanoes — are hypothetical features that are believed to be common throughout the outer solar system. These ice volcanoes are thought to erupt in a similar fashion to the volcanoes we have on Earth, but instead of molten rock, these volcanoes erupt ice-cold volatiles — like water, methane or ammonia. Dwarf planet Pluto, for example, has features that look like cryovolcanoes, as does Saturn’s moon Titan and Jupiter’s moon Ganymede. These locations are extremely cold and known to contain large quantities of methane and water, so internal heating (caused by radioactive decay or tidal processes) melt the ices and force them to the surface. When they vent through the crust, gases are released and the liquids quickly freeze and sublimate.

Around these vents, cryovolcanoes will grow, and if Ceres really does have its own ice volcanoes, this will be the closest planetary body to the sun (and Earth) known to have them.

Now, in research headed by the Max Planck Institute for Solar System Research (MPS) in Göttingen, Germany, scientists using Dawn data have, for the first time, taken a stab at dating the age of the bright material in the center of Occator Crater and realized that the location has likely been the site of many cryovolcanic eruptions in the recent past.

Occator Crater as observed by NASA’s Dawn spacecraft (NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

In the center of Occator, a pit measuring around 7 miles wide can be found, likely formed during the massive impact approximately 30 million years ago. But around the edges of that pit are mountains, some 750 meters high, and in the center is a cracked dome measuring 400 meters high and nearly 2 miles wide. This bright dome is called Cerealia Facula and surrounding it appears to be material that was spewed from a cryovolcanic vent. Analysis has shown that this material contains salts that were formed in the presence of water from Ceres’ interior and then deposited onto the surface. The minerals around Cerealia Facula has been dated to only four million years, meaning that there has been cryovolcanic eruptions long after the Occator impact punctured Ceres’ crust.

“The age and appearance of the material surrounding the bright dome indicate that Cerealia Facula was formed by a recurring, eruptive process, which also hurled material into more outward regions of the central pit,” said Andreas Nathues, lead investigator of Dawn’s Framing Camera. “A single eruptive event is rather unlikely.” As noted in an MPS news release, Jupiter moons Callisto and Ganymede have similar features that are also believed to be related to cryovolcanic eruptions.

“The large impact that tore the giant Occator crater into the surface of the dwarf planet must have originally started everything and triggered the later cryovolcanic activity,” added Nathues.

Previous imagery of haze inside Occator Crater has led to the suspicion that ices remain on the surface today; the haze could be vapor from sublimating water ice exposed on the surface having been forced to the surface from Ceres’ interior. Evidence for this haze has been supported by other studies and appears to vary throughout the day as one would expect — increased sunlight would accelerate sublimation (ice turning from a solid to a vapor without passing through the liquid phase).

If volatiles are still being extruded through this vent today, this would seem to indicate that, in addition to the cryovolcanic eruptions in the last four million years, some form of activity continues to this day. Add this to the recent discovery of organic material on Ceres’ surface, this small world has become a very big asset for planetary science.

For more on Ceres’ icy eruptions, check out one of my last DNews videos:

Mars’ Ancient Mega-Floods Are Still Etched Into the Red Planet

Around 3.5 billion years ago — when basic life was just gaining a foothold on Earth — the Tharsis region on Mars was swamped with vast floods that scar the landscape to this day.

perspective_view_towards_worcester_crater
Rendered perspective view of Worcester Crater using Mars Express elevation data. The dramatic crater rim was carved by the flow of ancient floodwater (ESA)

Mars wears its geological history like a badge of honor — ancient craters remain unchanged for hundreds of millions of years and long-extinct volcanoes look as if they were venting only yesterday. This is the nature of Mars’ thin, cold atmosphere; erosional processes that rapidly delete Earth’s geological history are largely absent on the Red Planet, creating a smorgasbord of features that provide planetary scientists with an open book on Mars’ ancient past.

In this latest observation from the European Mars Express mission, a flood of biblical proportions has been captured in all its glory. But this flood didn’t happen recently, this flood engulfed a vast plain to the north of the famous Valles Marineris region billions of years ago.

It is believed that a series of volcanic eruptions and tectonic upheavals in the Tharsis region caused several massive groundwater releases from Echus Chasma, a collection of valleys some 100 kilometers (62 miles) long and up to 4 kilometers (2.5 miles) deep. These powerful bursts of water carved vast outflow channels into the adjacent Lunae Planum, contributing to the formation of the Kasei Valles outflow channels, releasing water into the vast Chryse Planitia plains which acted as a “sink.” Smaller “dendritic” channels can be seen throughout the plain, indicating that there were likely many episodic bursts of water flooding the region.

This context image shows a region of Mars where Kasei Vallis empties into the vast Chryse Planitia (NASA MGS MOLA Science Team)
This context image shows a region of Mars where Kasei Vallis empties into the vast Chryse Planitia (NASA MGS MOLA Science Team)

These floods happened between 3.4 to 3.6 billion years ago, less than a billion years after the most basic lifeforms started to appear on Earth (a period of time known as the Paleoarchean era).

In the middle of what was likely a powerful, vast and turbulent flows of water is Worcester Crater that was created before the Tharsis floods and, though its crater rim stands to this day and retains its shape, it was obviously affected by the flow of water, with a “tail” of sediment downstream.

ESA Mars Express observation of the mouth of Kasei Valles, as it transitions into Chryse Planitia. The large crater in the lower left is Worcester Crater. (ESA/DLR/FU Berlin)
ESA Mars Express observation of the mouth of Kasei Valles, as it transitions into Chryse Planitia. The large crater in the lower left is Worcester Crater (ESA/DLR/FU Berlin)

Also of note are smaller “fresh” craters that would have appeared long after the flooding took place, excavating the otherwise smooth outflow channels. These younger craters have tails that seem to be pointed in the opposite direction of the flow of water. These tails weren’t caused by the flow of water, but by the prevailing wind direction.

From orbital observations by our armada of Mars missions, it is well known that these channels contain clays and other minerals associated with the long-term presence of water. Although the Red Planet is now a very dry place, as these beautiful Mars Express images show, this certainly hasn’t always been the case.

On Mars, There’s No Asphalt

Curiosity's right-middle and rear wheels, bearing the scars of 488 sols of rough roving. Credit: NASA/JPL-Caltech
Curiosity’s right-middle and rear wheels, bearing the scars of 488 sols of rough roving. Credit: NASA/JPL-Caltech

If you’re like me, you hang off every news release and new photo from our tenacious Mars rover Curiosity. The awesome one-ton, six-wheeled robot is, after all, exploring a very alien landscape. But if there’s one thing I’ve learned from the mission, Mars is far from being a truly alien place. Sure, we can’t breath the thin frigid air, but we can certainly recognize similar geological processes that we have on Earth, and, most intriguingly, regions that would have once been habitable for life as we know it. This doesn’t mean there was life, just that once upon a time parts of Gale Crater would have been pretty cozy for terrestrial microbes. Personally, I find that notion fascinating.

But, way back in May, I noticed something awry with our beloved rover’s wheels. Curiosity’s beautiful aircraft-grade aluminum wheels were looking rather beaten up. Punctures had appeared. Fearing the worst I reached out to NASA to find out what was going on. After a friendly email exchange with lead rover driver Matt Heverly, I felt a lot more at ease: The damage was predicted; dings, scratches, even holes were expected to appear in the thinnest (0.75 mm thick) aluminum between the treads. On Mars, after all, there is no asphalt. Also, erosion is a slower-paced affair in the thin winds and dry environment — sharp, fractured rocks protrude, embedding themselves into the wheels at every slow turn.

Then, on Friday, in a news update on Curiosity’s progress, JPL scientists mentioned that they would be commanding the rover to drive over a comparatively smooth patch to evaluate the condition of the wheels as their condition is getting worse. But isn’t that to be expected? Apparently not to this degree. “Dents and holes were anticipated, but the amount of wear appears to have accelerated in the past month or so,” said Jim Erickson, project manager for the NASA Mars Science Laboratory at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

So what are we looking at here?

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All of the wheels are exhibiting wear and tear, but this particular ‘rip’ in aluminum is by far the most dramatic. But what does that mean for Curiosity? We’ll have to wait and see once JPL engineers have assessed their condition. Although this kind of damage has inevitably been worked into the the structural equations for the wheels’ load-bearing capabilities, whichever way you look at it, damage like this is not good — especially as Curiosity hasn’t even roved three miles yet.

But in the spirit of Mars exploration, Curiosity will soldier on regardless of how rough the red planet treats her.

Read more in my coverage on Discovery News, a location you’ll find me during most daylight (and many nighttime) hours: