Category: Our Solar System (page 1 of 4)

Icy Moons and Their Plumes

The existence of water or water vapor plumes on Europa has been studied for years, with a consensus view that they do indeed exist.  Now NASA scientists have their best evidence so far that the moon does sporadically send water vapor into its atmosphere.  (NASA/ESA/K. Retherford/SWRI)

Just about everything that scientists see as essential for extraterrestrial life — carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur and sources of energy — is now known to be pretty common in our solar system and beyond.  It’s basically there for the taking  by untold potential forms of life.

But what is not at all common is liquid water.  Without liquid water Earth might well be uninhabited and today’s Mars, which was long ago significantly wetter, warmer and demonstrably habitable,  is widely believed to be uninhabited because of the apparent absence of surface water (and all that deadly radiation, too.)

This is a major reason why the discovery of regular plumes of water vapor coming out of the southern pole of Saturn’s moon Enceladus has been hailed as such a promising scientific development.  The moon is pretty small, but most scientists are convinced it does have an under-ice global ocean that feeds the plume and just might support biology that could be collected during a flyby.

But the moon of greatest scientific interest is Europa, one of the largest that orbits Jupiter.  It is now confidently described as having a sub-surface ocean below its crust of ice and — going back to science fiction writer extraordinaire Arthur C. Clarke — has often been rated the most likely body in our solar system to harbor extraterrestrial life.

That is why it is so important that years of studying Europa for watery plumes has now paid off.   While earlier observations strongly suggested that sporadic plumes of water vapor were in the atmosphere, only last month was the finding nailed, as reported in the journal Nature Astronomy.

“While scientists have not yet detected liquid water directly, we’ve found the next best thing: water in vapor form,” said Lucas Paganini, a NASA planetary scientist who led the water detection investigation.

 

As this cutaway shows, vents in Europa’s icy crust could allow plumes of water vapor to escape from a sub-surface ocean. If observed up close, the chemical components of the plumes would be identified and could help explain the nature and history of the ocean below. ( NASA) 

The amount of water vapor found in the European atmosphere wasn’t great — about an Olympic-sized pool worth of H2O.  … Read more

Mapping Titan, the Most Earth-Like Body in Our Solar System

In an image created by NASA’s Cassini spacecraft, sunlight reflects off lakes of liquid methane around Titan’s north pole.  Cassini radar and visible-light images allowed researchers to put together the first global geological map of Saturn’s largest moon.  (NASA/JPL-Caltech/University of Arizona/University of Idaho)

Saturn’s moon Titan has lakes and rivers of liquid hydrocarbons, temperatures that hover around -300 degrees Fahrenheit, and a thick haze that surrounds it and has cloaked it in mystery.   An unusual place for sure, but perhaps what’s most unusual is that Titan more closely resembles Earth of all the planets and moons in our solar system.

This is because like only Earth it has that flowing liquid on its surface, it has a climate featuring wind and rain that form dunes, rivers, lakes, deltas and seas (probably of filled with liquid methane and ethane), it has a thick atmosphere and it has weather patterns that change with the seasons.  The moon’s methane cycle is quite similar to our water cycle.

And now astronomers have used data from NASA’s Cassini-Huygens mission to map the entire surface of Titan for the first time.  Their work has found a global terrain of mountains, plains, valleys, craters and lakes .  Again, this makes Titan unlike anywhere else in the solar system other than Earth.

“Titan has an atmosphere like Earth. It has wind, it has rain, it has mountains,” said Rosaly Lopes, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena.  She and her colleagues wove together images and radar measurements taken by the spacecraft to produce the first global map of the moon.

“Titan has an active methane-based hydrologic cycle that has shaped a complex geologic landscape, making its surface one of most geologically diverse in the solar system,” she said.  “It’s a really very interesting world, and one of the best places in the solar system to look for life,”

Cassini orbited Saturn from 2004 to 2017 and collected vast amounts of information about the ringed gas giant and its moons. The mission included more than 100 fly-bys of Titan,  which allowed researchers to study the moon’s surface through its thick atmosphere and survey its terrain in unprecedented detail.

The first global geologic map of Titan is based on radar and visible-light images from NASA’s Cassini mission.

Their work, which now adds the surface of Titan to the kind of geological mapping done of the surfaces of Mars, Mercury and our moon, was published in Nature Astronomy.Read more

PIXL: A New NASA Instrument For Ferreting Out Clues of Ancient Life on Mars

 

Extremely high definition images of the com ponents of rocks and mud as taken by PIXL, the Planetary Instrument for X-ray Lithochemistry .   On the Mars 2020 rover, PIXL  will have significantly greater capabilities than previous similar instruments sent to Mars.  Rather than reporting bulk compositions averaged over several square centimeters, it will identify precisely where in the rock each element resides. With spatial resolution of about 300 micrometers, PIXL will conduct the first ever petrology investigations on Mars, correlating elemental compositions with visible rock textures . (NASA)J

The search for life, or signs of past life beyond Earth is now a central issue in space science, is central to the mission of NASA, and is actually a potentially breakthrough discovery in the making  for humanity.    The scientific stakes could hardly be higher.

But identifying evidence of ancient microbial life – and refuting all reasonable non-biological explanations for that evidence — is stunningly difficult.

As recent wrangling over Earth’s oldest rocks in Greenland has shown, determining the provenance of a deep-time biosignature even here on Earth is extraordinarily difficult. In 2016, scientists reported discovery of 3,700 million yr-old stromatolites in the Isua geological area of Greenland.

Just three years later, a field workshop held at the Isua discovery site brought experts from around the world to examine the intriguing structures and see whether the evidence cleared the very high bar needed to accept a biological interpretation. While the scientists who published the initial discovery held their ground, not one of the other scientists felt convinced by the evidence before them.  Watching and listening as the different scientists presented their cases was a tutorial in the innumerable factors involved in coming to any conclusion.

Now think about trying to wrestle with similar or more complex issues on Mars, of how scientists can reach of level of confidence to report that a sign (or hint) of past life has apparently been found.

As it turns out, the woman who led the Greenland expedition — Abigail Allwood of NASA’s Jet Propulsion Lab — is also one of the key players in the upcoming effort to find biosignatures on Mars.  She is the principal investigator of the Planetary Instrument for X-ray Lithochemistry (PIXL) that will sit on the extendable arm of the rover, and it has capabilities to see in detail the composition of Mars samples as never before.

The instrument has, of course, been rigorously tested to understand what it can and cannot do. … Read more

Hayabusa2 Snatches Second Asteroid Sample

Artist impression of the Hayabusa2 spacecraft touching down on asteroid Ryugu (JAXA / Akihiro Ikeshita)

“1… 2… 3… 4…”

The counting in the Hayabusa2 control room at the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Sciences (JAXA, ISAS) took on a rhythmic beat as everyone in the room took up the chant, their eyes fixed on the large display mounted on one wall.

“10… 11… 12… 13…”

The display showed the line-of-sight velocity (speed away from or towards the Earth) of the Hayabusa2 spacecraft. The spacecraft was about 240,000,000 km from the Earth where it was studying a near-Earth asteroid known as Ryugu. At this moment, the spacecraft was dropping to the asteroid surface to collect a sample of the rocky body.

“20… 21… 22… 23…”

Asteroid Ryugu from an altitude of 6km. Image was captured with the Optical Navigation Camera – Telescopic (ONC-T) on July 20, 2018 ( JAXA, University of Tokyo & collaborators)

Asteroid Ryugu is a carbonaceous or “C-type” asteroid; a class of small celestial bodies thought to contain organic material and undergone relatively little alteration since the beginning of the Solar System. Rocks similar to Ryugu would have pelted the early Earth, possibly delivering both water and the first ingredients for life to our young planet. Where and when these asteroids formed and how they moved through the Solar System is therefore a question of paramount importance to understanding how terrestrial planets like the Earth became habitable. It is a question not only tied to our own existence, but also to assessing the prospect of life elsewhere in the Universe.

The Hayabusa2 mission arrived at asteroid Ryugu just over one year ago at the end of June 2018. The spacecraft remotely analyzed the asteroid and deployed two rovers and a lander to explore the surface. Then in February of this year, the spacecraft performed its own descent to touchdown and collect a sample. The material gathered will be analyzed back on Earth when the spacecraft returns home at the end of 2020.

Touchdown is one of the most dangerous operation in the mission. The distances involved mean that it took about 19 minutes to communicate with the spacecraft during the first touchdown and 13 minutes during the second touchdown, when the asteroid had moved slightly closer to Earth. Both these durations are too long to manually guide the spacecraft to the asteroid surface.… Read more

Curiosity Rover as Seen From High Above by Mars Orbiter

A camera on board NASA’s Mars Reconnaissance Orbiter recently spotted the Curiosity rover in Gale Crater.  The image is color-enhanced to allow surface features to become more visible. (NASA/JPL-Caltech)

This is Apollo memory month, when the 50th anniversary arrives of the first landing of astronauts on the moon.  It was a very big deal and certainly deserves attention and applause.

But there’s something unsettling about the anniversary as well, a sense that the human exploration side of NASA’s mission has disappointed and that its best days were many decades ago.   After all, it has been quite a few years now since NASA has been able to even get an astronaut to the International Space Station without riding in a Russian capsule.

There have been wondrous (and brave) NASA human missions since Apollo — the several trips to the Hubble Space Telescope for emergency repair and upgrade come to mind — but many people who equate NASA with human space exploration are understandably dismayed.

This Many Worlds column does not focus on human space exploration, but rather on the science coming from space telescopes, solar system missions, and the search for life beyond Earth.

And as I have argued before, the period that following the last Apollo mission and began with the 1976 Viking landings on Mars has been — and continues to be — the golden era of space science.

This image of Curiosity,  which is now exploring an area that has been named Woodland Bay in Gale Crater, helps make the case.

Taken on May 31 by the HiRISE camera of NASA’s Mars Reconnaissance Orbiter (MRO), it shows the rover in a geological formation that holds remains of ancient clay.  This is important because clay can be hospitable to life, and Curiosity has already proven that Mars once had the water, organic compounds and early climate to support life.

The MRO orbits between 150 and 200 miles above Mars, so this detailed image is quite a feat.

The arm of the Curiosity rover examines the once-watery remains at Woodland Bay, Gale Crater. (NASA/JPL-Caltech)

Curiosity landed on Mars for what was planned as a mission of two years-plus. That was seven years ago this coming August.

The rover has had some ups and downs and has moved more slowly than planned, but it remains in motion — collecting paradigm-shifting information, drilling into the Mars surface, taking glorious images and making its way up the slopes of Gale Crater. … Read more

Methane on Mars. Here Today, Gone Tomorrow

On the 2,440th Martian day at Gale Crater, the Curiosity rover detected a large spike in the presence of the gas methane. It was by far the largest plume detected by the rover, and parallels an earlier ground-based discovery of an even larger plume of the gas.  (NASA, JPL-Caltech, MSSS)

The presence — and absence — of methane gas on Mars has been both very intriguing and very confusing for years.  And news coming out last week and then on Monday adds to this scientific mystery.

To the great surprise of the Curiosity rover team, their Sample Analysis on Mars instrument sent back a measurement of 21 parts per billion of methane on Thursday — by far the highest measurement since the rover landed at Gale Crater.

As Paul Mahaffy, principal investigator of the instrument that made the measurement, described it yesterday at a large astrobiology conference in Seattle, “We were dumbfounded.”

And then a few days later, all the methane was gone.   Mahaffy, and NASA headquarters, reported that the readings went down quickly to below 1 part per billion.

These perplexing findings are especially important because methane could — and also could not — be a byproduct of biology.  On Earth, more than 90 percent of methane is produced via biology.  On Mars — at this point, nobody knows.  But the question has certainly gotten scientists’ attention.

The most recent finding of a return to low methane levels suggests that last week’s methane detection was one of the transient methane plumes that have been observed in the past. While Curiosity scientists have noted background levels rise and fall seasonally, they haven’t found a pattern in the occurrence of these transient plumes.

“The methane mystery continues,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’re more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere.”

This image was taken by the left Navcam on the Curiosity Mars rover on June 18, 2019, the day when a methane plume was detected.  It shows part of “Teal Ridge,” which the rover has been studying within a region called the “clay-bearing unit.” (NASA/JPL-Caltech)

The nature and size of this most recent methane plume will, by chance, be the most widely observed so far.

That’s because the Mars Express orbiter happened to be performing spot tracking observations at the Gale Crater right around the time Curiosity detected the methane spike. … Read more

A Significant Advance: Primitive Earth Life Survives an 18-Month Exposure to Mars-Like Conditions in Space

The European Space Agency’s BIOMEX array, outside the Russian Zvezda module of the ISS. (ESA)

The question of whether simple life can survive in space is hardly new, but it has lately taken on a new urgency.

It is not only a pressing scientific question — might life from Mars or another body have seeded life on Earth?  Might organisms similar to extreme Earth life survive Mars-like conditions? — but it is also has some very practical implications.  If humans are going to some day land and live on the moon or on Mars, they will need to grow food to survive.

So the question is pretty basic:  can Earth seeds or dormant life survive a long journey to deep space and can they then  grow in the protected but still extreme radiation, temperature, and vacuum  of deep space?

It was with these questions in mind that the European Space Agency funded a proposal from the German Institute of Planetary Research to send samples of a broad range of simple to more complex life to the International Space Station in 2014, and to expose the samples to extreme conditions outside the station.

Some of the findings have been reported earlier,  but last month the full results of the Biomex tests (Biology on Mars Experiment) were unveiled in the journal Astrobiology.

And the answer is that many, though certainly not all, of the the samples of snow and permafrost algae, cyanobacteria, archaea, fungi, biofilms, moss and lichens in the  did survive their 533 days of living dangerous in their dormant states.  When brought back to Earth and returned to normal conditions, they returned to active life.

“For the majority of the chosen organisms, it was the first and the longest time they ever were exposed to space and Mars-like conditions,” Jean-Pierre Paul de Vera, principal investigator of the effort, wrote to me.  And the results were promising.

 

For the BIOMEX experiment, on 18 August 2014, Russian cosmonauts Alexander Skvortsov and Oleg Artemyev placed several hundred samples in an experiment container on the exterior of the Zvezda’Russian ISS module. The containers, open to the surrounding space environment, held primitive terrestrial organisms such as mosses, lichens, fungi, bacteria, archaea and algae, as well as cell membranes and pigments.

 

A microbiologist and planetary researcher at the German Space Agency’s Institute of Planetary Research in Berlin, de Vera and his team went from Antarctica to the parched Atacama desert in Chile, from the high Alps to the steppe highlands of central Spain to find terrestrial life surviving in extreme conditions (extremophiles.)

The samples were then placed in regolith (soil, dust and other rocky materials) simulated to be as close as possible to what is found on Mars.Read more

Ancient Mars Water. Ever More of It, and Flowing Ever Longer on the Surface

A photo of a preserved river channel on Mars with color overlaid to show different elevations (blue is low, yellow is high).
(Courtesy of NASA/JPL/Univ. Arizona/Univ. Chicago)

 

Rather like a swollen river overflowing its banks, the story of water on Mars keeps on rising and spreading in quite unpredictable ways.

While the planet is now inarguable parched — though with lots of polar and subsurface ice and, perhaps, some seasonal surface trickles — data from the Curiosity rover, the Mars Reconnaissance Orbiter and other missions have proven quite reliably that the planet was once much wetter and warmer.  But how much wetter, and for how long,  remains of subject of hot debate.

On one side, Mars climate modelers have struggled to find mechanisms to keep the planet wetter and warmer for more than it’s earliest period — perhaps 500 million years.  Their projections flow from the seemingly established conclusion that Mars lost much of its atmosphere by 3.5 billion years ago, and without that protection warmer and wetter appear to be impossible.

But the morphology of the planet, the gorges, the fossil lakes, the riverbeds and deltas that are visible  because of 21st century technology and missions,  appears to tell a different and more wide-ranging story of Mars water.

 

Mudstone at the “Kimberley” formation on Mars taken by NASA’s Curiosity rover. The strata in the foreground dip towards the base of Mount Sharp, indicating the ancient depression that existed before the larger bulk of the mountain formed.
Credit:NASA/JPL-Caltech/MSSS

And now, in one of the most expansive interpretations of the Martian water story, University of Chicago planetary scientist and Mars expert Edwin Kite and colleagues report in a Science Advances paper that the planet not only once had many, many lakes and rivers, but that they were filled as part of a water cycle involving precipitation, rather than primarily through the sporadic melting of primordial ice as a result of incoming meteorites or other astrophysical events.

What’s more, they write, the rivers continued to sporadically flow well past the time when the Martian surface has been assumed to be dead dry.

The era when Mars has been most often described as going from wet-to-dry is around 3.5 billion years ago, but their interpretation of when precipitation-filled rivers stopped running is about 3 billion years ago.  In other words, Kite’s team now says the rivers ran — often quite actively — for more than one billion years.… Read more

Japan’s Hayabusa2 Asteroid Mission Reveals a Remarkable New World

The Hayabusa2 touchdown movie, taken on February 22, 2019 (JST) when Hayabusa2 first touched down on asteroid Ryugu to collect a sample from the surface. It was captured using the onboard small monitor camera (CAM-H). The video playback speed is five times faster than actual time (JAXA).

On March 5 the Japan Aerospace Exploration Agency (JAXA) released the extraordinary video shown above. The sequence of 233 images shows a spacecraft descending to collect material from the surface of an asteroid, before rising amidst fragments of ejected debris. It is an event that has never been captured on camera before.

The images were taken by a camera onboard the Hayabusa2 spacecraft, a mission to explore a C-type asteroid known as “Ryugu” and bring a sample back to Earth.

C-type asteroids are a class of space rock that is thought to contain carbonaceous material and undergone little evolution since the early days of the Solar System. These asteroids may have rained down on the early Earth and delivered our oceans and possibly our first organics. Examination of the structure of Ryugu and its composition compared to Earth will help us understand how planets can become habitable.

Asteroid Ryugu from an altitude of 6km
Asteroid Ryugu from an altitude of 6km. Image was captured with the Optical Navigation Camera – Telescopic (ONC-T) on July 20, 2018 at around 16:00 JST. (JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, University of Aizu, AIST.)

Hayabusa2 arrived at asteroid Ryugu on June 27, 2018. The spacecraft spent the summer examining the asteroid with a suite of onboard instruments. Despite being a tiny world at only 1km across, Hayabusa2 spotted different seasons on Ryugu. Like the Earth, the asteroid’s rotation axis is inclined so that different levels of sunlight reach the northern and southern hemispheres.

It also rotated upside down, spinning in the opposite sense to the Earth and its own path around the Sun. This is likely indicative of a violent past, a view supported by the heavily bouldered and cratered surface. This rugged terrain presented the Hayabusa2 team with a problem: where could they land?

After a summer of observations, Hayabusa2 had been planning three different operations on the asteroid surface. The first was the deployment of two little rovers known as the MINERVA-II1. The second was the release of a shoebox-sized laboratory known as MASCOT, designed by the German and French space agencies.… Read more

The Gale Winds of Venus Suggest How Locked Exoplanets Could Escape a Fate of Extreme Heat and Brutal Cold

Two images of the nightside of Venus captured by the IR2 camera on the Akatsuki orbiter in September 2016 (JAXA).

 

More than two decades before the first exoplanet was discovered, an experiment was performed using a moving flame and liquid mercury that could hold the key to habitability on tidally locked worlds.

The paper was published in a 1969 edition of the international journal, Science, by researchers Schubert and Whitehead. The pair reported that when a Bunsen flame was rotated beneath a cylindrical container of mercury, the liquid began to flow around the container in the opposite direction at speeds up to four times greater than the rotation of the flame. The scientists speculated that such a phenomenon might explain the rapid winds on Venus.

On the Earth, the warm equator and cool poles set up a pressure difference that creates our global winds. These winds are deflected westward by the rotation of the planet (the so-called Coriolis force) promoting a zonal (east-west) air flow around the globe. But what would happen if our planet’s rotation slowed? Would our winds just cycle north and south between the equator and poles?

The Moon is tidally locked to the Earth, so only one hemisphere is visible from our planet (Smurrayinchester / wikipedia commons).

Such a slow-rotating scenario may be the lot of almost all rocky exoplanets discovered to date. Planets such as the TRAPPIST-1 system and Proxima Centauri-b all orbit much closer to their star than Mercury, making their faint presence easier to detect but likely resulting in tidal lock. Like the moon orbiting the Earth, planets in tidal lock have one side permanently facing the star, creating a day that is equal to the planet’s year.

The dim stars orbited by these planets can mean they receive a similar level of radiation as the Earth, placing them within the so-called “habitable zone.” However, tidal lock comes with the risk of horrific atmospheric collapse. On the planet side perpetually facing away from the star, temperatures can drop low enough to freeze an Earth-like atmosphere. The air from the dayside would then rush around the planet to fill the void, freezing in turn and causing the planet to lose its atmosphere even within the habitable zone.

The only way this could be prevented is if winds circulating around the planet could redistribute the heat sufficiently to prevent freeze-out. But without a strong Coriolis force from the planet’s rotation, can such winds exist?… Read more

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