Artist’s concept of Kraken Mare, the largest methane lake or sea on Saturn’s large moon Titan. This moon is the only known body in space, besides Earth, known to have stable bodies of liquid (albeit not water) on its surface. Image via Cornell University/ NASA.

Earth is a water planet. Titan – Saturn’s largest moon – is the only other body in our solar system, in fact the only other body we know, anywhere, to have liquids on its surface. Titan has rain, rivers and even lakes and seas, not made of water, but instead composed of liquid methane (the primary constituent of natural gas) and ethane. Some of Titan’s lakes and seas have significant depth, too, and now a new study announced by researchers at Cornell University shows that Titan’s largest sea is at least 1,000 feet – 300 meters – deep in its center. As the researchers pointed out, that’s:

… enough room for a potential robotic submarine to explore.

The new peer-reviewed findings were published in the Journal of Geophysical Research on December 4, 2020.

The results come from the study of data from the Cassini mission, which orbited Saturn, weaving among its moons, from 2004 to 2017. The new research is based primarily on data from one of the probe’s last flybys of Titan. The depth of all the lakes and seas had been estimated, except for one: Kraken Mare, the largest Titanian sea. As outlined in the paper:

From 2013 to 2017, we have been probing the depth of Titan’s methane-dominated seas by penetrating the liquid with Cassini’s radar altimeter. The depth and composition of each of the seas had already been derived, except for Titan’s largest sea Kraken Mare. Herein, we describe the final observation of this campaign before the end of Cassini in 2017.

Radar was needed because Titan is completely covered by a dense smog-like haze. Lead author Valerio Poggiali noted:

The depth and composition of each of Titan’s seas had already been measured, except for Titan’s largest sea, Kraken Mare, which not only has a great name [it’s named for a legendary sea monster], but also contains about 80% of the moon’s surface liquids.

Cassini acquired this infrared view of seas and lakes in Titan’s northern hemisphere in 2014. Sunlight can be seen glinting off the southern part of Titan’s largest sea, Kraken Mare. This alien sea is almost as large as all 5 of the Great Lakes in North America, combined. Image via NASA/ JPL-Caltech/ University of Arizona/ University of Idaho.

The initial data about Kraken Mare had been obtained by Cassini on August 21, 2014, during the T104 flyby. Cassini used its radar from an altitude of nearly 600 miles (nearly 1,000 km), to observe Ligeia Mare (a smaller sea near Titan’s North Pole), Kraken Mare and Moray Sinus, an estuary at the northern end of Kraken Mare.

Moray Sinus was found to be about 280 feet (85 meters) deep, but the central part of Kraken Mare was too deep for the radar to measure all the way to the bottom.

The composition of Kraken Mare, however – mostly methane with ethane mixed in – provided clues. If it was similar to that of Moray Sinus, as would be expected, then data analysis indicated that the central part of Kraken Mare must be at least 328 feet (100 meters) deep and probably closer to 1,000 feet (305 meters).

Radar map from Cassini showing Kraken Mare and other nearby seas and lakes on Titan. Image via JPL-Caltech/ NASA/ ASI/ USGS/ Science News.

At some point in the future, NASA wants to send a submarine, called Titan Sub, to explore Kraken Mare. What might it find? Artist’s concept via NASA.

Kraken Mare is also huge in terms of size, almost as large as all five of the Great Lakes in North America, combined.

These new results will help scientists learn more about Titan’s lakes and seas, of course. Plus they’ll gain insights on how Titan’s eerily similar – yet very alien – hydrologic cycle works. Poggiali said:

In this context, to understand the depth and composition of Kraken Mare and the Moray Sinus is important because this enables a more precise assessment of Titan’s methane hydrology. Still, we have to solve many mysteries.

Now about the potential for a future submarine exploring the depths of Titan’s largest sea. It’s an idea for the future, but maybe this study will bring it closer. Scientists have suggested sending a submarine-like probe – tentatively called Titan Sub – to investigate Kraken Mare firsthand. Imagine actually exploring an alien sea? How cool would that be? As Poggiali noted, this data will be valuable in planning for such a mission:

Thanks to our measurements, scientists can now infer the density of the liquid with higher precision, and consequently better calibrate the sonar aboard the vessel and understand the sea’s directional flows.

Scientists think that Titan is similar to what the early Earth was like, around the time when life was just starting to evolve. It could, therefore, provide valuable data about how life originated on Earth, or at least prebiotic chemistry.

Valerio Poggiali at Cornell University, lead author of the new study. Image via Cornell University.

So, could there be anything living in those lakes and seas? It’s an exciting thought, but it would have to be a form of life, even if just microscopic, unlike any on Earth, using methane instead of water to survive. Titan’s atmosphere is mostly nitrogen, like Earth’s, but the moon is extremely cold on the surface – about -290 degrees Fahrenheit (-179 degrees Celsius) – which is why its hydrology is based on liquid methane and ethane instead of water. On Titan, water ice is as hard as rock.

There’ve also been suggestions of a water ocean below Titan’s surface, similar to those thought to exist on Jupiter’s moon Europa and Saturn’s moon Enceladus, but, if it exists, little is known about it so far.

Bottom line: A new study of data from NASA’s Cassini mission shows that Titan’s largest methane sea, Kraken Mare, is at least 1,000 feet (300 meters) deep near its center.

Source: The Bathymetry of Moray Sinus at Titan’s Kraken Mare

Via Cornell University

Source:
https://earthsky.org/space/titans-largest-sea-kraken-mare-is-1000-feet-deep

The Cassini spacecraft – which gave us dramatic images of Saturn and its rings and moons while orbiting this world from 2004 to 2017, caught this image of Titan in front of Saturn’s rings. The moon’s hazy atmosphere makes it appear like a fuzzy ball against the sharp rings of Saturn. Image via NASA/ JPL-Caltech/ Space Science Institute.

Titan is the largest moon of Saturn, the seventh planet outward from our sun. It’s the only moon in our solar system known to have a thick atmosphere, and it’s the only only known body in space, besides Earth, known to have stable bodies of surface liquid. Titan has a kind of hydrological cycle, much like Earth’s, with liquids falling from the sky and flowing across this moon’s surface before evaporating back into clouds. Some of the weather phenomena we’d be familiar with on Titan include dust storms and monsoonal rains. Earth’s atmosphere is 78% nitrogen; Titan’s is 98% nitrogen. Titan’s climate is driven by seasonal change. So you can see that, in some ways, the closest comparison to Titan’s atmosphere is the one we know best: Earth’s.

But there are also many differences between Earth and this distant Saturnian moon, showing how alien and strange it would be to experience the weather on Titan.

Titan is 10 times farther from the sun than Earth and receives 100 times less solar energy. It orbits roughly in the plane of Saturn’s equator, and its tilt relative to the plane of our solar system is about the same as Saturn’s. As on Earth, Saturn’s seasons – and Titan’s – are caused by their tilts, which cause the sun to strike the different hemispheres of these worlds more strongly or more weakly throughout Saturn’s year. Saturn takes 29 years to orbit the sun once; its year is 29 Earth-years long. Thus both Saturn and Titan have seasons lasting more than 7 Earth-years.

And so any given spot on Titan experiences a change in weather at a much slower pace than on Earth.

An equinox on Titan – when both hemispheres of this moon are receiving the sun’s rays about equally – occurs about every 15 years. The last Titan equinox was in 2009. We now know – thanks to the Cassini mission to Saturn, which arrived in 2004 and lasted until 2017 – that powerful wind storms roved across Titan around the time of its 2008 equinox, producing soot that fell like rain and creating dunes on Titan’s surface.

In general, it’s now thought that Titan’s winds flow in a pole-to-pole circulation for some 12 Earth years before taking a few years to transition to the opposite direction as winter changes to summer.

This animation is based on images captured by Cassini’s Visual and Infrared Mapping Spectrometer during several Titan flybys in 2009 and 2010. It shows clear bright spots appearing close to Titan’s equator around the time of its equinox, which scientists have interpreted as dust storms. The brightenings were visible for only a short period of time – between 11 hours to five Earth weeks – and cannot be seen in previous or subsequent images. Image via ESA/ NASA/ JPL-Caltech/ University of Arizona.

Soot deposited into dunes reveals the patterns of the wind on Titan’s surface. Image via NASA/ JPL-Caltech/ ASI/ Université Paris-Diderot.

Titan’s solstices come every 15 years, too. The last one was in 2017, bringing the longest day of summer to Titan’s northern hemisphere and the shortest day of winter to its southern hemisphere. NASA’s stated goal for Cassini’s second extended mission was to keep the spacecraft in orbit until the solstice, which happened in May of that year, and to observe seasonal changes in the Saturn system along the way. In fact, Cassini’s Solstice Mission was the name of Cassini’s second extended mission, which ended with a dramatic plunge of the spacecraft into Saturn’s clouds in September 2017.

And that’s why we know so much about the seasons, and the weather, on Titan!

Thanks to Cassini, we know that the clouds on Titan are composed mostly of methane and ethane, which are hydrocarbons. But it’s not just the clouds that are composed of methane. Lakes on Titan’s surface are made of methane too. Scientists believe that cryovolcanoes (ice volcanoes) erupt and spew methane into Titan’s atmosphere, which then rains down onto the surface, forming lakes.

Liquid methane is the dominant force behind Titan’s weather and surface erosion. During the Cassini mission, scientists saw ripples and waves on the surface of Titan’s lakes, indicating that winds may be stronger during Titan’s summer. And, by the way, because Titan is a less massive world than Earth, with weaker gravity, waves on its surface lakes would be seven times taller and three times slower!

This near-infrared color image shows reflection off of a hydrocarbon lake on Titan. The bright white area is the glint off the lake. The pink is haze illuminated from below by reflection off the lake. The faint pink color coming from just above the reflection has been suggested to represent the first waves seen on Titan, and thus the first sea-surface waves ever detected outside Earth. Image via NASA/ JPL-Caltech/ University of Arizona/ University of Idaho.

Titan’s rains, when they fall, appear to have a monsoon-like effect on the surface, with downpours that shape alluvial fans. Alluvial fans are roughly triangular features made of sediments deposited by flowing water or even glaciers. These landform features are seen on places such as Titan, Earth and Mars.

Yet Titan’s downpours are rare. They probably only occur once every Titanian year, or once every 29 Earth-years.

In 2016, Cassini imaged a shiny spot covering more than 46,000 square miles (120,000 square km) that had not been in previous images and was not seen in subsequent images. It appears that Cassini caught freshly fallen liquid-methane rain that then drained into a nearby lake, Kraken Mare. This lake, which had been discovered by Cassini in 2008, is the largest body of surface liquid on Titan.

One unique feature of Titan’s atmosphere is that – with its combination of raindrops and sunlight – it should have occasional displays of rainbows. Because the raindrops on Titan are made of methane, and refraction for liquid methane differs from water, the rainbows would be larger than what we see on Earth. Sunlight does not penetrate the atmosphere easily due to Titan’s thick haze; however, another type of rainbow would actually be more common: an infrared rainbow.

Titan’s atmosphere is mostly clear at infrared wavelengths (this is why Cassini could easily see surface features on Titan with its infrared camera). Visitors to Titan could view these infrared rainbows with night-vision goggles.

Our views of Titan before Cassini showed just its hazy atmosphere, obscuring the surface and any possible activity on the ground. The mission not only peeled back this layer of atmosphere while analyzing its elements and interactions, but it also showed us the effect that atmosphere has on this moon’s surface.

Bottom line: Titan is the only moon in the solar system with a thick atmosphere. It has four seasons as Earth does, and a cycle similar to Earth’s hydrological cycle.

Source:
https://earthsky.org/space/titan-saturns-moon-weather-seasons-methane-rain-storms

Source: https://www.livescience.com/saturn-moon-titan-sea-1000-feet-deep.html

Source:
https://www.newscientist.com/article/2265635-puzzling-signal-on-saturns-moon-rhea-may-finally-be-explained/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home

President-elect of the United States Joe Biden speaking with supporters at a community event at Sun City MacDonald Ranch in Henderson, Nevada. Image via Planetary Society/ Gage Skidmore.

Shortly before 4 a.m. (12:00 UTC) last week (January 7, 2021), Congress confirmed Democrat Joe Biden as the United States presidential election winner. Vice President Mike Pence, presiding over the joint session, announced the tally, 306-232. Whatever your political leanings, if you are a space fan, you watched closely during the Donald Trump administration as it supported NASA’s long-term goal of sending astronauts to Mars. And you saw our nation’s course change during Trump’s tenure to a short-term goal of returning the next man and first woman to the moon by 2024, with the Artemis program. Overall – under Donald Trump – America’s gaze shifted more strongly to human missions to the moon and to Mars. Will that focus continue under President Joe Biden? How can NASA expect to fare under Biden?

Here is some context. In 2017, Trump appointed Jim Bridenstine, a Republican congressman from Oklahoma, to run NASA. The Congress – and the science and space communities – were caught off guard because NASA is typically run by a scientist or a former astronaut or other apolitical space expert. Bridenstine was eventually confirmed by the Senate in April 2018, more than seven months after his appointment. Despite his lack of space or science background, in two years as NASA administrator he appeared to gain the respect of many. Immediately after Biden’s election, however, in early November 2020, Bridenstine announced he would resign.

More context. The wonderful missions out into our solar system that we hear so much about – the much-loved Mars fleet, New Horizons’ dramatic sweep past Pluto, Cassini’s 13 years at Saturn and so on – are robotic missions. The workhorse missions to understand our own Earth and sun are robotic missions. There’s been a decades-long attempt to balance the smaller robotic missions like these, which bear so much fruit, with the bigger, flashier, more expensive missions that could carry human beings into the solar system. The decision to launch a Cassini or a New Horizons has to be made decades in advance; indeed, some of the most visible and stirring robotic missions of this century so far were the lifetime work of scientists begun in the last decades of the 20th century. Why can’t we have both kinds of missions? Why indeed? But it does seem that – in terms of the space program since it began in the late 1950s – the focus has shifted between human missions and robotic missions. That’s just something to bear in mind.

How will the U.S. space program change under a President Joe Biden? Biden is a known quantity in many ways, having served for decades in the Senate and eight years as vice president in the Obama administration. But his plans for NASA and America’s space program are less clear.

The Biden campaign made little mention of its space priorities, apart from a few statements made during the Crew Dragon Demo 2 launch on May 30, 2020, the first launch of NASA astronauts from American soil since 2011. Specifically, Biden wrote on his website:

As president, I look forward to leading a bold space program that will continue to send astronaut heroes to expand our exploration and scientific frontiers through investments in research and technology to help millions of people here on Earth.

The Democratic Party platform – a practical list of Democratic Party objectives for the next four years – was proposed to the 2020 Platform Committee at its meeting on July 27, 2020. While thorough in its claims to upholding national health, economic growth, and racial equity, among other things, its only mention of the space program was condensed to a few lines. However brief, it was considered to be promising in the opinion of John Logsdon, the founder of George Washington University’s Space Policy Institute. The Democratic platform not only endorsed NASA’s current plans, but mentioned its priorities ranging from science and technology development to continued operation of the International Space Station and human space exploration:

Democrats continue to support NASA and are committed to continuing space exploration and discovery. We believe in continuing the spirit of discovery that has animated NASA’s human space exploration, in addition to its scientific and medical research, technological innovation, and educational mission that allows us to better understand our own planet and place in the universe. We will strengthen support for the United States’ role in space through our continued presence on the International Space Station, working in partnership with the international community to continue scientific and medical innovation. We support NASA’s work to return Americans to the moon and go beyond to Mars, taking the next step in exploring our solar system. Democrats additionally support strengthening NASA and the National Oceanic and Atmospheric Administration’s Earth observation missions to better understand how climate change is impacting our home planet.

From what we can gather, two major impending changes are likely.

First, a Biden administration could strengthen NASA and NOAA’s Earth-observing capabilities, with the goal of better understanding climate change. Lori Garver, the NASA deputy administrator during the Obama administration, was a key speaker at the SpaceVision 2020 convention on November 7 and 8, 2020. She said:

Managing the Earth’s ability to sustain human life and biodiversity will likely, in my view, dominate a civil space agenda for a Biden-Harris administration.

Second, although it supports a human return to the moon, a Biden administration has made no specific mention of launch dates. Launching humans to the moon in 2024 as part of the Artemis mission was the Trump administration’s timeline. There is speculation that the Biden administration will, at the very least, slow down the Artemis program, perhaps freeing up money for Earth science and other priorities elsewhere in the agency. On December 20, 2020, the United States government’s two houses of Congress agreed on NASA’s final budget for fiscal year 2021. In the report accompanying the bill, Senate appropriators noted that the looming uncertainty “makes it difficult to analyze the future impacts that funding the accelerated moon mission will have on NASA’s other important missions.” Wendy Whitman Cobb, associate professor of Strategy and Security Studies, U.S. Air Force School of Advanced Air and Space Studies, said

I don’t think Artemis will get canceled. I also don’t think it will get any more money than what it’s currently getting.

On November 10, the Biden administration announced the rosters of the agency review teams that will fan out across the federal government to gather information and guide the Biden administration’s planning. Garver, who led the Obama administration’s transition, commented:

The transition teams really come in to see how things are doing and make recommendations going forward.

NASA chief Jim Bridenstine speaking in December 2019, in front of the newly completed SLS core stage for the Artemis 1 mission. Days after Joe Biden’s November election, Bridenstine announced his January 20, 2021, resignation. Who will replace him? Image via Wikimedia Commons.

A key priority of Biden’s space focus will be his selection of a new NASA administrator. He has so far been quiet about his choice, but there’s been plenty of speculation concerning potential candidates. That list is dominated by women. For example, Pam Melroy, a former NASA astronaut who flew on three shuttle missions, is a likely choice. Other possibilities include Wanda Austin, former president and chief executive of the Aerospace Corporation, and Gretchen McClain, a former NASA official who later worked in industry and serves on the boards of several companies.

Past transitions suggest that a new administrator for NASA might not come until months after the January 20 inauguration. After being inaugurated in January 2009, President Obama didn’t nominate Charlie Bolden as administrator (and Garver as deputy administrator) until May 2009; the Senate confirmed them in July. Bridenstine, despite emerging as a top candidate for NASA administrator days after Trump won the presidential election in November 2016, was only nominated in September 2017.

Artist’s concept of an astronaut on the moon, gazing back at Earth, via NASA’s Artemis program.

Bottom line: Democrat Joe Biden will be the next U.S. President. What are his plans for NASA and America’s space program? We predict a focus on Earth observation, especially that related to climate change. And we join many others in predicting that the goal of launching the next man and first woman to the moon in the Artemis program will be pushed back from 2024.

Read more from EarthSky: NASA announces 18 astronauts on its Artemis Team

Via Democratic Party Platform

Source:
https://earthsky.org/human-world/how-will-the-u-s-space-program-fare-under-joe-biden

This movie, created by NASA/JPL back in 2009, is a compilation of 61 images taken by the Cassini spacecraft. Over a decade later, it’s still lovely!

Via NASA/Youtube

EarthSky 2021 lunar calendars now available! Order today. Going fast!

Source:
https://earthsky.org/space/saturn-moon-ballet-nutcracker-suite-video

Source:
https://phys.org/news/2020-12-potentially-diverse-metabolic-menu-enceladus.html

Composite image of Io and Jupiter (Jupiter image from the Cassini spacecraft, Io image from the new research). Sulfur dioxide plumes from Io’s volcanoes are seen in yellow. Image via ALMA (ESO/ NAOJ/ NRAO)/ I. de Pater et al./ NRAO/ AUI NSF/ S. Dagnello/ NASA/ ESA/ UC Berkeley.

Io, one of the four large Galilean moons of Jupiter, is the most volcanically active body in our solar system, even more so than Earth. It has over 400 active volcanoes and is often described as hellish. Io also has an extremely thin atmosphere, composed mostly of sulfur dioxide (SO2). This little world’s volcanoes regularly spew sulfur dioxide into its atmosphere. Still, scientists weren’t sure whether the atmosphere stems from hot sulfur dioxide coming directly from the volcanoes, or cold sulfur dioxide which accumulates on Io’s surface and freezes before sublimating into the atmosphere. Now they’ve determined it’s both.

The 2021 lunar calendars are here! Order yours before they’re gone. Makes a great gift!

Using the ALMA telescope in Chile, researchers at the University of California, Berkeley have announced that up to half of the sulfur dioxide in Io’s atmosphere comes directly from its volcanoes. The results have been published in two new peer-reviewed papers accepted for publication in The Planetary Science Journal, which you can read here and here.

Astronomer Imke de Pater, who led the study, said in a statement:

It was not known which process drives the dynamics in Io’s atmosphere. Is it volcanic activity, or gas that sublimates from the icy surface when Io is in sunlight? What we show is that, actually, volcanoes do have a large impact on the atmosphere.

The answer, it turns out, is both.

Some of the sulfur dioxide does indeed freeze out onto the surface, the researchers found. This happens when Io passes through Jupiter’s shadow every 42 hours. When Io was being observed by the researchers on March 20, 2018, they noticed that radio emissions from the sulfur dioxide dropped exponentially. This meant that Io’s lower atmosphere, 6-12 miles (10-20 km) in altitude, collapsed and froze onto the surface.

The temperature during this period fell to -270 degrees Fahrenheit (-168 degrees Celsius), cold enough for sulfur dioxide to freeze. Io’s surface is typically about -230 degrees Fahrenheit (-150 degrees Celsius). Cold, but not quite cold enough for the sulfur dioxide to freeze out.

On September 2 and 11, 2018, the sulfur dioxide emissions rose again within 10 minutes after Io emerged from Jupiter’s shadow back into sunlight. De Pater said:

As soon as Io gets into sunlight, the temperature increases, and you get all this SO2 ice subliming into gas, and you reform the atmosphere in about 10 minutes’ time, faster than what models had predicted.

That explains where some of the frozen sulfur dioxide comes from. But the researchers noticed something else as well. ALMA detected abundant sulfur dioxide over the volcanoes, as well as low levels of the gas globally in Io’s atmosphere. This suggested that the more widespread gas was originating from unseen or “stealth” volcanoes. They emit sulfur dioxide, but not other smoke or particles that can be easily seen.

Right now, the researchers think that extra gas is coming from such stealth volcanoes, although they couldn’t completely rule out the possibility that it could be sulfur dioxide that isn’t completely condensing out onto the surface. As de Pater noted:

The SO2 that we see with ALMA when Io is in eclipse is at a very low level, and we can’t say if that is stealth volcanism or caused by SO2 not completely condensing out.

Io, as seen by the Galileo spacecraft on September 19, 1997. Image via NASA/ JPL/ University of Arizona/ NASA Photojournal.

Earlier observations from the Keck Observatory from last July, however, supported the stealth volcanism scenario. Keck detected abundant sulfur monoxide (SO) over the volcanoes, as well as widespread in the atmosphere. The researchers say that sunlight breaks the sulfur-oxygen bond in the sulfur dioxide that has been ejected hundreds of kilometers above the surface, creating the sulfur monoxide. De Pater said:

But then, when we looked at the SO with Keck, we can only explain the SO emissions, which are widespread on the surface, through this stealth volcanism, because excitation of the SO requires a very high temperature.

By observing Io in its orbit around Jupiter as it moved into and then out of Jupiter’s shadow, the researchers were able to figure out how much of the moon’s sulfur dioxide deposits came from freezing out on the surface and how much came from stealth or other volcanoes. Statia Luszcz-Cook from Columbia University in New York said:

When Io passes into Jupiter’s shadow, and is out of direct sunlight, it is too cold for sulfur dioxide gas, and it condenses onto Io’s surface. During that time, we can only see volcanically-sourced sulfur dioxide. We can, therefore, see exactly how much of the atmosphere is impacted by volcanic activity.

A volcanic eruption on Io, caught by Galileo’s cameras on June 28, 1997. Image via NASA.

A closer look from Galileo at one of Io’s volcanoes, called Pele, as it was erupting. Image via NASA/ JPL/ USGS.

By using ALMA, scientists were able to “see,” for the first time, plumes of both sulfur dioxide and sulfur monoxide coming up from Io’s volcanoes. Two of those volcanoes, Karei Patera and Daedalus Patera, were erupting in March, and a third volcano was active in September.

The researchers now calculate that 30% to 50% of Io’s atmosphere is produced directly by active volcanoes.

A third gas, potassium chloride (KCI), was also detected by ALMA, and is a common component of lava. According to Luszcz-Cook:

We see KCI in volcanic regions where we do not see SO2 or SO. This is strong evidence that the magma reservoirs are different under different volcanoes.

Katherine de Kleer at the California Institute of Technology added:

By studying Io’s atmosphere and volcanic activity, we can understand more about the volcanoes, the tidal heating process and Io’s interior.

The volcano Loki Patera, as seen by Voyager 1 in 1979. The dark U-shaped feature is a lava lake about 124 miles (200 km) across. Image via NASA/ JPL/ USGS/ Planetary Science Institute.

Infrared view of Io’s active volcanoes from NASA’s Juno spacecraft, currently orbiting Jupiter. Wow! Image via NASA/ JPL-Caltech/ SwRI/ INAF/ The Planetary Society.

The scientists are eager to learn more about Io’s magma as well, and are planning to observe the moon at additional radio wavelengths. These can probe several inches beneath the surface and provide clues about what Io’s magma is composed of and its temperature. They also want to know more about the temperature of Io’s lower atmosphere. De Pater said:

To measure the temperature of Io’s atmosphere, we need to obtain a higher resolution in our observations, which requires that we observe the moon for a longer period of time. We can only do this when Io is in sunlight, since it does not spend much time in eclipse. During such an observation, Io will rotate by tens of degrees. We will need to apply software that helps us make unsmeared images. We have done this previously with radio images of Jupiter made with ALMA and the Very Large Array.

How can a small moon like Io, way out in the outer solar system, have active volcanoes? Io is volcanically active due to tidal heating. The same side of Io faces Jupiter, just like the same side of the moon always faces Earth. The gravitational pull of Jupiter, as well as the moons Europa and Ganymede, creates tremendous friction and heating inside Io.

Io was last observed up close by NASA’s Galileo mission in the late 1990s/early 2000s. The current Juno orbiter has seen Io from farther away, but its primary mission is to observe Jupiter itself in detail as it orbits the giant planet. It has taken some cool images from a distance though.

Imke de Pater at the University of California, Berkeley, who lead the new study. Image via UC Berkeley.

The new results help to solve the mystery of how Io’s atmosphere forms and how its volcanoes play a major part in that. But there are still many more questions to be answered – and new ones to be asked – about the solar system’s most active volcanic hotspot.

Bottom line: Active volcanoes produce almost half of Io’s sulfur atmosphere, according to new observations using ALMA.

Source: ALMA Observations of Io Going into and Coming out of Eclipse

Source: High Spatial and Spectral Resolution Observations of the Forbidden 1.707 um Rovibronic SO Emissions on Io: Evidence for Widespread Stealth Volcanism*

Via UC Berkeley

Via NRAO

Source:
https://earthsky.org/space/io-sulfur-volcanoes-hot-so2-cold-so2

Source:
https://phys.org/news/2020-10-impact-craters-reveal-titan-dynamic.html

Infrared images of Saturn’s moon Enceladus, as seen by the Cassini spacecraft, which orbited Saturn, weaving in among its moons from 2004 to 2017. A new analysis of Cassini date shows that Enceladus’ north pole might be resurfaced by fresh ice deposits. In this image, the famous tiger stripes fissures – from which water erupts in strange alien geysers – can also be seen at the moon’s south pole. Image via NASA/ JPL-Caltech/ University of Arizona/ LPG/ CNRS/ University of Nantes/ Space Science Institute.

Saturn’s moon Enceladus is famous for the huge water-vapor geysers at its south pole, which are thought to originate from a global ocean deep beneath the moon’s outer ice crust. At this moon’s south pole, water is seen to comes up to the surface through giant cracks in the ice called tiger stripes. As the water vapor re-freezes in Enceladus’ extremely tenuous atmosphere, it forms ice particles that fall back down and coat the moon’s south polar region with fresh ice. Until now, this kind of activity was seen only at the moon’s south pole. Now that has changed.

Now, scientists studying new global mosaic infrared images of Enceladus, taken by NASA’s Cassini spacecraft, have announced that they’ve found the first evidence that the moon’s north pole has also been painted with a fresh coat of ice fairly recently, geologically-speaking.

Weak geysers at this pole could be the reason. Or the fresh ice might be due to water forced up from the subsurface ocean through cracks in the moon’s icy crust.

The new peer-reviewed study was published in the October 2020 issue of Icarus.

The famous geysers of water vapor at Enceladus’ south pole erupt through huge cracks in the icy surface. Now scientists have evidence that the moon’s north polar region is also geologically active, although on a smaller scale. The plumes contain water vapor, ice particles, salts, methane, silica, molecular hydrogen and a variety of simple and complex organic molecules. Image via NASA/ JPL-Caltech/ Space Science Institute.

The new infrared images, from Cassini’s Visible and Infrared Mapping Spectrometer (VIMS), are the most detailed ever made of Enceladus’ surface, from data sent back by the Cassini mission, which ended in September 2017. The researchers found that, surprisingly, the moon’s north polar region also showed evidence of resurfacing by ice, even though it lacks any known geysers or tiger stripe-like fissures. This may be caused by as-yet unseen geysers or a more gradual movement of ice through fractures in the crust, from the subsurface ocean to the surface. Gabriel Tobie, VIMS scientist with the University of Nantes in France and co-author of the new paper, said in a statement:

The infrared shows us that the surface of the south pole is young, which is not a surprise because we knew about the jets that blast icy material there.

Now, thanks to these infrared eyes, you can go back in time and say that one large region in the northern hemisphere appears also young and was probably active not that long ago, in geologic timelines.

VIMS collected light reflected off Saturn, its rings and its ten largest icy moons. This was both visible light that can be seen by human eyes as well as infrared light, which tells scientists more about the makeup of the material reflecting it.

Enceladus’ geysers originate from the subsurface ocean, venting through cracks in the icy surface at the south pole. They coat the surface with fresh layers of ice. Are there as-yet unseen plumes at the moon’s north pole as well? Image via NASA/ JPL-Caltech/ SwRI.

A closer visible light image of Enceladus’ north pole, taken by Cassini on November 27, 2016. The terrain is much more cratered than in the south, but the infrared images in the new study – and the cracks in the surface seen here – show that there has been at least some geological activity in the region. Image via NASA/ JPL-Caltech.

Enceladus’ geysers were first spotted by Cassini back in 2005, and ever since then the moon has fascinated scientists and the public alike as to its potentially for being a habitable world. This was especially true after Cassini later confirmed that the water was originating from a global salty ocean beneath the icy surface, similar to Europa.

Additional studies have shown that the ocean is similar to Earth’s oceans in terms of salinity, and there is even evidence for active geothermal vents on the ocean floor. On Earth, such such vents – like “black smokers” – are oases for a diverse population of life forms in the otherwise very dark and cold ocean depths.

Last January, scientists at the Southwest Research Institute (SwRI) announced that they had developed a new geochemical model of Enceladus that showed the interior of the small moon is more complex than previously thought, including carbon dioxide being controlled by chemical reactions on the seafloor of the ocean. Those findings open up intriguing new possibilities for life in Enceladus’ subsurface watery abyss.

Lead author Christopher Glein of SwRI said in a statement:

By understanding the composition of the plume, we can learn about what the ocean is like, how it got to be this way and whether it provides environments where life as we know it could survive. We came up with a new technique for analyzing the plume composition to estimate the concentration of dissolved CO2 in the ocean. This enabled modeling to probe deeper interior processes.

Gabriel Tobie, VIMS scientist at the University of Nantes and co-author of the new study. Image via LPG.

During its mission, Cassini flew through through the water vapor plumes several times, analyzing what is in them. The spacecraft found water vapor, ice particles, salts, methane, silica (SiO2), molecular hydrogen (H2) and a variety of simple and complex organic molecules. Since this is basically seawater being spewn out into space, this provides important clues as to what conditions are like in the ocean. So far, all signs point to an ocean that is quite habitable by earthly standards. This doesn’t prove there is life there yet, but the evidence indicates there well could be.

The infrared images from Cassini are providing new clues about how geologically active Enceladus is, not only at its south pole with the dramatic watery plumes, but elsewhere on the this little icy world as well.

Bottom line: A new study of infrared images of Saturn’s moon Enceladus shows that the moon’s north pole is geologically active.

Source: Photometrically-corrected global infrared mosaics of Enceladus: New implications for its spectral diversity and geological activity

Via Jet Propulsion Laboratory

Source:
https://earthsky.org/space/fresh-ice-enceladus-north-pole-geologic-activity