Are There Enough Chemicals on Icy Worlds to Support Life?

For decades, scientists have believed that there could be life beneath the icy surface of Jupiter’s moon Europa. Since that time, multiple lines of evidence have emerged that suggest that it is not alone. Indeed, within the Solar System, there are many “ocean worlds” that could potentially host life, including Ceres, Ganymede, Enceladus, Titan, Dione, Triton, and maybe even Pluto.

But what if the elements for life as we know it are not abundant enough on these worlds? In a new study, two researchers from the Harvard Smithsonian Center of Astrophysics (CfA) sought to determine if there could in fact be a scarcity of bioessential elements on ocean worlds. Their conclusions could have wide-ranging implications for the existence of life in the Solar System and beyond, not to mention our ability to study it.

The study, titled “Is extraterrestrial life suppressed on subsurface ocean worlds due to the paucity of bioessential elements?” recently appeared online. The study was led by Manasvi Lingam, a postdoctoral fellow at the Institute for Theory and Computation (ITC) at Harvard University and the CfA, with the support of Abraham Loeb – the director of the ITC and the Frank B. Baird, Jr. Professor of Science at Harvard.

Artist’s depiction of a watery exoplanet orbiting a distant red dwarf star. Credit: CfA

In previous studies, questions on the habitability of moons and other planets have tended to focus on the existence of water. This has been true when it comes to the study of planets and moons within the Solar System, and especially true when it comes the study of extra-solar planets. When they have found new exoplanets, astronomers have paid close attention to whether or not the planet in question orbits within its star’s habitable zone.

This is key to determining whether or not the planet can support liquid water on its surface. In addition, astronomers have attempted to obtain spectra from around rocky exoplanets to determine if water loss is taking place from its atmosphere, as evidenced by the presence of hydrogen gas. Meanwhile, other studies have attempted to determine the presence of energy sources, since this is also essential to life as we know it.

In contrast, Dr. Lingam and Prof. Loeb considered how the existence of life on ocean planets could be dependent on the availability of limiting nutrients (LN). For some time, there has been considerable debate as to which nutrients would be essential to extra-terrestrial life, since these elements could vary from place to place and over timescales. As Lingam told Universe Today via email:

“The mostly commonly accepted list of elements necessary for life as we know it comprises of hydrogen, oxygen, carbon, nitrogen and sulphur. In addition, certain trace metals (e.g. iron and molybdenum) may also be valuable for life as we know it, but the list of bioessential trace metals is subject to a higher degree of uncertainty and variability.”

Artist rendering showing an interior cross-section of the crust of Enceladus, which shows how hydrothermal activity may be causing the plumes of water at the moon’s surface. Credits: NASA-GSFC/SVS, NASA/JPL-Caltech/Southwest Research Institute

For their purposes, Dr. Lingam and Prof. Loeb created a model using Earth’s oceans to determine how the sources and sinks – i.e. the factors that add or deplete LN elements into oceans, respectively – could be similar to those on ocean worlds. On Earth, the sources of these nutrients include fluvial (from rivers), atmospheric and glacial sources, with energy being provided by sunlight.

Of these nutrients, they determined that the most important would be phosphorus, and examined how abundant this and other elements could be on ocean worlds, where conditions as vastly different. As Dr. Lingam explained, it is reasonable to assume that on these worlds, the potential existence of life would also come down to a balance between the net inflow (sources) and net outflow (sinks).

“If the sinks are much more dominant than the sources, it could indicate that the elements would be depleted relatively quickly. In other to estimate the magnitudes of the sources and sinks, we drew upon our knowledge of the Earth and coupled it with other basic parameters of these ocean worlds such as the pH of the ocean, the size of the world, etc. known from observations/theoretical models.”

While atmospheric sources would not be available to interior oceans, Dr. Lingam and Prof. Loeb considered the contribution played by hydrothermal vents. Already, there is abundant evidence that these exist on Europa, Enceladus, and other ocean worlds. They also considered abiotic sources, which consist of minerals leached from rocks by rain on Earth, but would consist of the weathering of rocks by these moons’ interior oceans.

Artist’s rendering of possible hydrothermal activity that may be taking place on and under the seafloor of Enceladus. Credit: NASA/JPL

Ultimately, what they found was that, unlike water and energy, limiting nutrients might be in limited supply when it comes to ocean worlds in our Solar System:

“We found that, as per the assumptions in our model, phosphorus, which is one of the bioessential elements, is depleted over fast timescales (by geological standards) on ocean worlds whose oceans are neutral or alkaline in nature, and which possess hydrothermal activity (i.e. hydrothermal vent systems at the ocean floor). Hence, our work suggests that life may exist in low concentrations globally in these ocean worlds (or be present only in local patches), and may therefore not be easily detectable.”

This naturally has implications for missions destined for Europa and other moons in the outer Solar System. These include the NASA Europa Clipper mission, which is currently scheduled to launch between 2022 and 2025. Through a series of flybys of Europa, this probe will attempt to measure biomarkers in the plume activity coming from the moon’s surface.

Similar missions have been proposed for Enceladus, and NASA is also considering a “Dragonfly” mission to explore Titan’s atmosphere, surface and methane lakes. However, if Dr. Lingam and Prof. Loeb’s study is correct, then the chances of these missions finding any signs of life on an ocean world in the Solar System are rather slim. Nevertheless, as Lingam indicated, they still believe that such missions should be mounted.

Artist’s concept of a Europa Clipper mission. Credit: NASA/JPL

“Although our model predicts that future space missions to these worlds might have low chances of success in terms of detecting extraterrestrial life, we believe that such missions are still worthy of being pursued,” he said. “This is because they will offer an excellent opportunity to: (i) test and/or falsify the key predictions of our model, and (ii) collect more data and improve our understanding of ocean worlds and their biogeochemical cycles.”

In addition, as Prof. Loeb indicated via email, this study was focused on “life as we know it”. If a mission to these worlds did find sources of extra-terrestrial life, then it would indicate that life can arise from conditions and elements that we are not familiar with. As such, the exploration of Europa and other ocean worlds is not only advisable, but necessary.

“Our paper shows that elements that are essential for the ‘chemistry-of-life-as-we-know-it’, such as phosphorous, are depleted in subsurface oceans,” he said. “As a result, life would be challenging in the oceans suspected to exist under the surface ice of Europa or Enceladus. If future missions confirm the depleted level of phosphorous but nevertheless find life in these oceans, then we would know of a new chemical path for life other than the one on Earth.”

In the end, scientists are forced to take the “low-hanging fruit” approach when it comes to searching for life in the Universe . Until such time that we find life beyond Earth, all of our educated guesses will be based on life as it exists here. I can’t imagine a better reason to get out there and explore the Universe than this!

Further Reading: arXiv

There was Evidence for Europa’s Geysers Hiding in Plain Sight in Old Spacecraft Data From 1997

Jupiter’s moon Europa continues to fascinate and amaze! In 1979, the Voyager missions provided the first indications that an interior ocean might exist beneath it’s icy surface. Between 1995 and 2003, the Galileo spaceprobe provided the most detailed information to date on Jupiter’s moons to date. This information bolstered theories about how life could exist in a warm water ocean located at the core-mantle boundary.

Even though the Galileo mission ended when the probe crashed into Jupiter’s atmosphere, the spaceprobe is still providing vital information on Europa. After analyzing old data from the mission, NASA scientists have found independent evidence that Europa’s interior ocean is venting plumes of water vapor from its surface. This is good news for future mission to Europa, which will attempt to search these plumes for signs of life.

The study which describes their findings, titled “Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures“, recently appeared in the journal Nature Astronomy. The study was led by Xianzhe Jia, a space physicist from the Department of Climate and Space Sciences and Engineering at the University of Michigan, and included members from UCLA and the University of Iowa.

Artist’s concept of the Galileo space probe passing through the Jupiter system. Credit: NASA

The data was collected in 1997 by Galileo during a flyby of Europa that brought it to within 200 km (124 mi) of the moon’s surface. At the time, its Magnetometer (MAG) sensor detected a brief, localized bend in Jupiter’s magnetic field, which remained unexplained until now. After running the data through new and advanced computer models, the team was able to create a simulation that showed that this was caused by interaction between the magnetic field and one of the Europa’s plumes.

This analysis confirmed ultraviolet observations made by NASA’s Hubble Space Telescope in 2012, which suggested the presence of water plumes on the moon’s surface. However, this new analysis used data collected much closer to the source, which indicated how Europa’s plumes interact with the ambient flow of plasma contained within Jupiter’s powerful magnetic field.

In addition to being the lead author on this study, Jia is also the co-investigator for two instruments that will travel aboard the Europa Clipper mission – which may launch as soon as 2022 to explore the moon’s potential habitability. Jia’s and his colleagues were inspired to reexamine data from the Galileo mission thanks to Melissa McGrath, a member of the SETI Institute and also a member of the Europa Clipper science team.

During a presentation to her fellow team scientists, McGrath highlighted other Hubble observations of Europa. As Jiang explained in a recent NASA press release:

“The data were there, but we needed sophisticated modeling to make sense of the observation. One of the locations she mentioned rang a bell. Galileo actually did a flyby of that location, and it was the closest one we ever had. We realized we had to go back. We needed to see whether there was anything in the data that could tell us whether or not there was a plume.”

Artist’s impression of a water vapor plume on Europa. Credit: NASA/ESA/K. Retherford/SWRI

When they first examined the information 21 years ago, the high-resolution data obtained by the MAG instrument showed something strange. But it was thanks to the lessons provided by the Cassini mission, which explored the plumes on Saturn’s moon Enceladus, that the team knew what to look for. This included material from the plumes which became ionized by the gas giant’s magnetosphere, leaving a characteristic blip in the magnetic field.

After reexamining the data, they found that the same characteristic bend (localized and brief) in the magnetic field was present around Europa. Jia’s team also consulted data from Galileo’s Plasma Wave Spectrometer (PWS) instrument to measure plasma waves caused by charged particles in gases around Europa’s atmosphere, which also appeared to back the theory of a plume.

This magnetometry data and plasma wave signatures were then layered into new 3D modeling developed by the team at the University of Michigan (which simulated the interactions of plasma with Solar system bodies). Last, they added the data obtained from Hubble in 2012 that suggested the dimensions of the potential plumes. The end result was a simulated plume that matched the magnetic field and plasma signatures they saw in the Galileo data.

As Robert Pappalardo, a Europa Clipper project scientist at NASA’s Jet Propulsion Laboratory (JPL), indicated:

“There now seem to be too many lines of evidence to dismiss plumes at Europa. This result makes the plumes seem to be much more real and, for me, is a tipping point. These are no longer uncertain blips on a faraway image.” 

Artist’s concept of a Europa Clipper mission, which will study Europa in 2022-2025 to search for signs of life. Credit: NASA/JPL

The findings are certainly good news for the Europa Clipper mission, which is expected to make the journey to Jupiter between 2022 and 2025. When this probe arrives in the Jovian system, it will establish an orbit around Jupiter and conduct rapid, low-altitude flybys of Europa. Assuming that plume activity does take place on the surface of the moon, the Europa Clipper will sample the frozen liquid and dust particles for signs of life.

“If plumes exist, and we can directly sample what’s coming from the interior of Europa, then we can more easily get at whether Europa has the ingredients for life,” Pappalardo said. “That’s what the mission is after. That’s the big picture.”

At present, the mission team is busy looking at potential orbital paths for the Europa Clipper mission. With this new research in hand, the team will choose a path that will take the spaceprobe above the plume locations so that it is in an ideal position to search them for signs of life. If all goes as planned, the Europa Clipper could be the first of several probes that finally proves that there is life beyond Earth.

And be sure to check out this video of the Europa Clipper mission, courtesy of NASA:

Further Reading: NASA, Nature

Could There be Alien Life Right Beneath the Surface of Icy Worlds Like Enceladus and Europa?

For decades, scientists have been speculating that life could exist in beneath the icy surface of Jupiter’s moon Europa. Thanks to more recent missions (like the Cassini spacecraft), other moons and bodies have been added to this list as well – including Titan, Enceladus, Dione, Triton, Ceres and Pluto. In all cases, it is believed that this life would exist in interior oceans, most likely around hydrorthermal vents located at the core-mantle boundary.

One problem with this theory is that in such undersea environments, life might have a hard time getting some of the key ingredients it would need to thrive. However, in a recent study – which was supported by the NASA Astrobiology Institute (NAI) – a team of researchers ventured that in the outer Solar System, the combination of high-radiation environments, interior oceans and hydrothermal activity could be a recipe for life.

The study, titled “The Possible Emergence of Life and Differentiation of a Shallow Biosphere on Irradiated Icy Worlds: The Example of Europa“, recently appeared in the scientific journal Astrobiology. The study was led by Dr. Michael Russell with the support of Alison Murray of the Desert Research Institute and Kevin Hand – also a researcher with NASA JPL.

Vestimentiferan tubeworms (Riftia pachyptila) found near the Galapagos islands. Credit: NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011.

For the sake of their study, Dr. Russell and his colleagues considered how the interaction between alkaline hydrothermal springs and sea water is often considered to be how the key building blocks for life emerged here on Earth. However, they emphasize that this process was also dependent on energy provided by our Sun. The same process could have happened on moon’s like Europa, but in a different way. As they state in their paper:

“[T]he significance of the proton and electron flux must also be appreciated, since those processes are at the root of life’s role in free energy transfer and transformation. Here, we suggest that life may have emerged on irradiated icy worlds such as Europa, in part as a result of the chemistry available within the ice shell, and that it may be sustained still, immediately beneath that shell.”

In the case of moon’s like Europa, hydrothermal springs would be responsible for churning up all the necessary energy and ingredients for organic chemistry to take place. Ionic gradients, such as oxyhydroxides and sulfides, could drive the key chemical processes – where carbon dioxide and methane are hydrogenated and oxidized, respectively – which could lead to the creation of early microbial life and nutrients.

At the same time, the heat from hydrothermal vents would push these microbes and nutrients upwards towards the icy crust. This crust is regularly bombarded by high-energy electrons created by Jupiter’s powerful magnetic field, a process which creates oxidants. As scientists have known for some time from surveying Europa’s crust, there is a process of exchange between the moon’s interior ocean and its surface.

Artist’s concept of plume activity on the surface of Europa. Credit: NASA/JPL-Caltech

As Dr. Russell and his colleagues indicate, this action would most likely involve the plume activity that has been observed on Europa’s surface, and could lead to a network of ecosystems on the underside of Europa’s icy crust:

“Models for transport of material within Europa’s ocean indicate that hydrothermal plumes could be well constrained within the ocean (primarily by the Coriolis force and thermal gradients), leading to effective delivery through the ocean to the ice-water interface. Organisms fortuitously transported from hydrothermal systems to the ice-water interface along with unspent fuels could potentially access a larger abundance of oxidants directly from the ice. Importantly, oxidants might only be available where the ice surface has been driven to the base of the ice shell.”

As Dr. Russel indicated in an interview with Astrobiology Magazine, microbes on Europa could reach densities similar to what has been observed around hydrothermal vents here on Earth, and may bolster the theory that life on Earth also emerged around such vents. “All the ingredients and free energy required for  life are all focused in one place,” he said. “If we were to find life on Europa, then that would strongly support the submarine alkaline vent theory.”

This study is also significant when it comes to mounting future missions to Europa. If microbial ecosystems exist on the undersides of Europa’s icy crust, then they could be explored by robots that are able to penetrate the surface, ideally by traveling down a plume tunnel. Alternately, a lander could simply position itself near an active plume and search for signs of oxidants and microbes coming up from the interior.

Artist’s impression of a hypothetical ocean cryobot (a robot capable of penetrating water ice) in Europa. Credit: NASA

Similar missions could also be mounted to Enceladus, where the presence of hydrothermal vents has already been confirmed thanks to the extensive plume activity observed around its southern polar region. Here too, a robotic tunneler could enter surface fissures and explore the interior to see if ecosystems exist on the underside of the moon’s icy crust. Or a lander could position itself near the plumes and examine what is being ejected.

Such missions would be simpler and less likely to cause contamination than robotic submarines designed to explore Europa’s deep ocean environment. But regardless of what form a future mission to Europa, Enceladus, or other such bodies takes, it is encouraging to know that any life that may exist there could be accessible. And if these missions can sniff it out, we will finally know that life in the Solar System evolved in places other than Earth!

Further Reading: Astrobiology Magazine, Astrobiology

NASA Says James Webb Telescope will Study Solar System’s “Ocean Worlds”

In October of 2018, the James Webb Space Telescope (JWST) will be launched into orbit. As part of NASA’s Next Generation Space Telescope program, the JWST will spend the coming years studying every phase of cosmic history. This will involve probing the first light of the Universe (caused by the Big Bang), the first galaxies to form, and extra-solar planets in nearby star systems.

In addition to all of that, the JWST will also be dedicated to studying our Solar System. As NASA recently announced, the telescope will use its infrared capabilities to study two “Ocean Worlds” in our Solar System – Jupiter’s moon Europa and Saturn’s moon Enceladus. In so doing, it will add to observations previously made by NASA’s Galileo and Cassini orbiters and help guide future missions to these icy moons.

The moons were chosen by scientist who helped to develop the telescope (aka. guaranteed time observers) and are therefore given the privilege of being among the first to use it. Europa and Enceladus were added to the telescope’s list of targets since one of the primary goals of the telescope is to study the origins of life in the Universe. In addition to looking for habitable exoplanets, NASA also wants to study objects within our own Solar System.

Artist rendering showing an interior cross-section of the crust of Enceladus, which shows how hydrothermal activity may be causing the plumes of water at the moon’s surface. Credits: NASA-GSFC/SVS, NASA/JPL-Caltech/Southwest Research Institute

One of the main focuses will be on the plumes of water that have been observed breaking through the icy surfaces of Enceladus and Europa. Since 2005, scientists have known that Enceladus has plumes that periodically erupt from its southern polar region, spewing water and organic chemicals that replenish Saturn’s E-Ring. It has since discovered that these plumes reach all the way into the interior ocean that exists beneath Enceladus’ icy surface.

In 2012, astronomers using the Hubble Space Telescope detected similar plumes coming from Europa. These plumes were spotted coming from the moon’s southern hemisphere, and were estimated to reach up to 200 km (125 miles) into space. Subsequent studies indicated that these plumes were intermittent, and presumably rained water and organic materials from the interior back onto the surface.

These observations were especially intriguing since they bolstered the case for Europa and Enceladus having interior, warm-water oceans that could harbor life. These oceans are believed to be the result of geological activity in the interior that is caused by tidal flexing. Based on the evidence gathered by the Galileo and Cassini orbiters, scientists have theorized that these surface plumes are the result of these same geological processes.

The presence of this activity could also means that these moons have hydrothermal vents located at their core-mantle boundaries. On Earth, hydrothermal vents (located on the ocean floor) are believed to have played a major role in the emergence of life. As such, their existence on other bodies within the Solar System is viewed as a possible indication of extra-terrestrial life.

The effort to study these “Ocean Worlds” will be led by Geronimo Villanueva, a planetary scientist at NASA’s Goddard Space Flight Center. As he explained in a recent NASA press statement, he and his team will be addressing certain fundamental questions:

“Are they made of water ice? Is hot water vapor being released? What is the temperature of the active regions and the emitted water? Webb telescope’s measurements will allow us to address these questions with unprecedented accuracy and precision.”

Villanueva’s team is part of a larger effort to study the Solar System, which is being led by Heidi Hammel – the executive VP of the Association of Universities for Research in Astronomy (AURA). As she described the JWST’s “Ocean World” campaign to Universe Today via email:

We will be seeking signatures of plume activity on these ocean worlds as well as active spots. With the near-infrared camera of NIRCAM, we will have just enough spatial resolution to distinguish general regions of the moons that could be “active” (creating plumes). We will also use spectroscopy (examining specific colors of light) to sense the presence of water, methane and several other organic species in plume material.”

Possible spectroscopy results from one of Europa’s water plumes. This is an example of the data the Webb telescope could return. Credit: NASA-GSFC/SVS/Hubble Space Telescope/Stefanie Milam/Geronimo Villanueva

To study Europa, Villanueva and his colleagues will take high-resolution imagery of Europa using the JWST’s near-infrared camera (NIRCam). These will be used to study the moon’s surface and search for hot spots that are indicative of plumes and geological activity. Once a plume is located, the team will determine its composition using Webb’s near-infrared spectrograph (NIRSpec) and mid-infrared instrument (MIRI).

For Enceladus, the team will be analyze the molecular composition of its plumes and perform a broad analysis of its surface features. Due to its small size, high-resolution of the surface will not be possible, but this should not be a problem since the Cassini orbiter already mapped much of its surface terrain. All told, Cassini has spent the past 13 years studying the Saturn system and will conclude the “Grande Finale” phase of its mission this September 15th.

These surveys, it is hoped, will find evidence of organic signatures in the plumes, such as methane, ethanol and ethane. To be fair, there are no guarantees that the JWST’s observations will coincide with plumes coming from these moons, or that the emissions will have enough organic molecules in them to be detectable. Moreover, these indicators could also be caused by geological processes.

Nevertheless, the JWST is sure to provide evidence that will allow scientists to better characterize the active regions of these moons. It is also anticipated that it will be able to pinpoint locations that will be of interest for future missions, such as NASA’s Europa Clipper mission. Consisting of an orbiter and lander, this mission – which is expected to launch sometime in the 2020s – will attempt to determine if Europa is habitable.

As Dr. Hammel explained, the study of these two “Ocean Moons” is also intended to advance our understanding about the origins of life in the Universe:

“These two ocean moons are thought to provide environments that may harbor water-based life as we know it.  At this point, the issue of life elsewhere is completely unknown, though there is much speculation.  JWST can move us closer to understanding these potentially habitable environments, complementing robotic spacecraft missions that are currently in development (Europa Clipper) and may be planned for the future.   At the same time, JWST will be examining the far more distant potentially habitable environments of planets around other stars.  These two lines of exploration – local and distant – allow us to make significant advances in the search for life elsewhere.”

Once deployed, the JWST will be the most powerful space telescope ever built, relying on eighteen segmented mirrors and a suite of instruments to study the infrared Universe. While it is not meant to replace the Hubble Space Telescope, it is in many ways the natural heir to this historic mission. And it is certainly expected to expand on many of Hubble’s greatest discoveries, not the least of which are here in the Solar System.

Be sure to check out this video on the kinds of spectrographic data the JWST will provide in the coming years, courtesy of NASA:

Further Reading: NASA

Europa Lander Could Carry a Microphone and “Listen” to the Ice to Find Out What’s Underneath

Between the Europa Clipper and the proposed Europa Lander, NASA has made it clear that it intends to send a mission to this icy moon of Jupiter in the coming decade. Ever since the Voyager 1 and 2 probes conducted their historic flybys of the moon in 1973 and 1974 – which offered the first indications of a warm-water ocean in the moon’s interior – scientists have been eager to peak beneath the surface and see what is there.

Towards this end, NASA has issued a grant to a team of researchers from Arizona State University to build and test a specially-designed seismometer that the lander would use to listen to Europa’s interior. Known as the Seismometer for Exploring the Subsurface of Europa (SESE), this device will help scientists determine if the interior of Europa is conducive to life.

According to the profile for the Europa Lander, this microphone would be mounted to the robotic probe. Once it reached the surface of the moon, the seismometer would begin collecting information on Europa’s subsurface environment. This would include data on its natural tides and movements within the shell, which would determine the icy surface’s thickness.

Image of Europa’s ice shell, taken by the Galileo spacecraft, of fractured “chaos terrain”. Credit: NASA/JPL-Caltech

It would also determine if the surface has pockets of water – i.e. subsurface lakes – and see how often water rises to the surface. For some time, scientists have suspected that Europa’s “chaos terrain” would be the ideal place to search for evidence of life. These features, which are basically a jumbled mess of ridges, cracks, and plains, are believed to be spots where the subsurface ocean is interacting with the icy crust.

As such, any evidence of organic molecules or biological organisms would be easiest to find there. In addition, astronomers have also detected water plumes coming from Europa’s surface. These are also considered to be one of the best bets for finding evidence of life in the interior. But before they can be explored directly, determining where reservoirs of water reside beneath the ice and if they are connected to the interior ocean is paramount.

And this is where instruments like the SESE would come into play. Hongyu Yu is an exploration system engineer from ASU’s School of Earth and Space Exploration and the leader of the SESE team. As he stated in a recent article by ASU Now, “We want to hear what Europa has to tell us. And that means putting a sensitive ‘ear’ on Europa’s surface.”

While the idea of a Europa Lander is still in the concept-development stage, NASA is working to develop all the necessary components for such a mission. As such, they have provided the ASU team with a grant to develop and test their miniature seismometer, which measures no more than 10 cm (4 inches) on a side and could easily be fitted aboard a robotic lander.

Europa’s “Great Lake.” Scientists speculate many more exist throughout the shallow regions of the moon’s icy shell. Credit: Britney Schmidt/Dead Pixel FX/Univ. of Texas at Austin.

More importantly, their seismometer differs from conventional designs in that it does not rely on a mass-and-spring sensor. Such a design would be ill-suited for a mission to another body in our Solar System since it needs to be positioned upright, which requires that it be carefully planted and not disturbed. What’s more, the sensor needs to be placed within a complete vacuum to ensure accurate measurements.

By using a micro-electrical system with a liquid electrolyte for a sensor, Yu and his team have created a seismometer that can operate under a wider range of conditions. “Our design avoids all these problems,” he said. “This design has a high sensitivity to a wide range of vibrations, and it can operate at any angle to the surface. And if necessary, they can hit the ground hard on landing.”

As Lenore Dai – a chemical engineer and the director of the ASU’s School for Engineering of Matter, Transport and Energy – explained, the design also makes the SESE well suited for exploring extreme environments – like Europa’s icy surface. “We’re excited at the opportunity to develop electrolytes and polymers beyond their traditional temperature limits,” she said. “This project also exemplifies collaboration across disciplines.”

The SESE can also take a beating without compromising its sensor readings, which was tested when the team struck it with a sledgehammer and found that it still worked afterwards. According to seismologist Edward Garnero, who is also a member of the SESE team, this will come in handy. Landers typically have six to eight legs, he claims, which could be mated with seismometers to turn them into scientific instruments.

Artist’s concept of chloride salts bubbling up from Europa’s liquid ocean and reaching the frozen surface.  Credit: NASA/JPL-Caltech

Having this many sensors on the lander would give scientists the ability to combine data, allowing them to overcome the issue of variable seismic vibrations recorded by each. As such, ensuring that they are rugged is a must.

“Seismometers need to connect with the solid ground to operate most effectively. If each leg carries a seismometer, these could be pushed into the surface on landing, making good contact with the ground. We can also sort out high frequency signals from longer wavelength ones. For example, small meteorites hitting the surface not too far away would produce high frequency waves, and tides of gravitational tugs from Jupiter and Europa’s neighbor moons would make long, slow waves.”

Such a device could also prove crucial to missions other “ocean worlds” within the Solar System, which include Ceres, Ganymede, Callisto, Enceladus, Titan and others. On these bodies as well, it is believed that life could very well exist in warm-water oceans that lie beneath the surface. As such, a compact, rugged seismometer that is capable of working in extreme-temperature environments would be ideal for studying their interiors.

What’s more, missions of this kind would be able to reveal where the ice sheets on these bodies are thinnest, and hence where the interior oceans are most accessible. Once that’s done, NASA and other space agencies will know exactly where to send in the probe (or possibly the robotic submarine). Though we might have to wait a few decades on that one!

Further Reading: ASU Now

This Is The Highest Resolution Image Of Europa We Have … For Now

This is the highest resolution image taken by Galileo at Europa — Jupiter’s 4th largest moon — until our next mission to the planet. It was obtained at an original image scale of 19 feet (6 meters) per pixel. The gray line down the middle resulted from missing data that was not transmitted by Galileo. Credit: NASA/JPL-Caltech

In the movie 2010: The Year We Make Contact, the sequel to Stanley’s Kubrick’s 2001: A Space Odyssey, black Monoliths multiply, converge and transform Jupiter into a new star. We next hear astronaut David Bowman’s disembodied voice with this message: “All these worlds are yours except Europa. Attempt no landing there.” The newborn sun warms Europa, transforming the icy landscape into a primeval jungle. At the end, a single Monolith appears in the swamp, waiting once again to direct the evolution of intelligent life forms.

Europa’s cracked, icy surface imaged by NASA’s Galileo spacecraft in 1998. Credit: NASA/JPL-Caltech/SETI Institute

Stay away from Europa? No way. It’s just too fascinating a place with its jigsaw-puzzle ice sheets, crisscross valleys, miles of ice on top and a warm, salty ocean below. The movie was prescient — if you’re going to search for life elsewhere in the solar system, Europa’s one of the best candidates.

While we’ve sent spacecraft to photograph and study the icy moon during orbital flybys, no lander has yet to touch the surface. That may change soon. In early 2016, in response to a congressional directive, NASA’s Planetary Science Division began a pre-Phase A study to assess the science value and engineering design of a future Europa lander mission. In June 2016, NASA convened a 21-member team of scientists for the Science Definition Team (SDT). The team put together set of science objectives and measurements for the mission concept and submitted the report to NASA on Feb. 7.

This artist’s rendering illustrates a conceptual design for a potential future mission to land a robotic probe on the surface of Jupiter’s moon Europa. The lander is shown with a sampling arm extended, having previously excavated a small area on the surface. The circular dish on top is a combo high-gain antenna and camera mast, with stereo imaging cameras mounted on the back of the antenna. Three vertical shapes located around the top center of the lander are attachment points for cables that would lower the rover from a sky crane, the planned landing system for this mission concept. Credits: NASA/JPL-Caltech

The report lists three science goals for the mission. The primary goal is to search for evidence of life on Europa. The other goals are to determine the habitability of Europa by directly analyzing material from the surface, and to characterize the surface and subsurface to support future robotic exploration of Europa and its ocean.

This image from NASA’s Galileo spacecraft show the intricate detail of Europa’s icy surface. The red staining occurs in areas where briny waters from below — possibly mixed with sulfur — reach the surface. Radiation from Jupiter bombards the material, causing it to redden. Gravitational flexing of the moon as it orbits Jupiter fractures the icy crust into a chaotic landscape of snaking valleys and ice sheets. It also warms the ocean beneath the crust, potentially making it habitable. Credit: NASA/JPL-Caltech

The evidence is quite strong that Europa, with a diameter of 1,945 miles — slightly smaller than Earth’s moon —  has a global saltwater ocean beneath its icy crust. This ocean has at least twice as much water as Earth’s oceans. Two things make Europa’s ocean unique and give the moon a greater chance of supporting microbial life compared to say, Ganymede and Enceladus, which also hold water reservoirs beneath their crusts.

Astronomers hypothesize that chloride salts bubble up from the icy moon’s global liquid ocean and reach the frozen surface where they are bombarded with sulfur from volcanoes on Jupiter’s innermost large moon Io. Molecular signs of life may be transported where they could be detected by a spacecraft.  In this illustration, we see Europa (foreground), Jupiter (right) and Io (middle). Credit: NASA/JPL-Caltech

One: the ocean is relatively close to the surface, just 10-15 miles below the moon’s icy shell. Radiation from Jupiter (high-speed electrons and protons) bombards ice, sulfur and salts on the surface to create compounds that could trickle down into warmer regions and used by living things for growth and metabolism.

Broken plates and blocks of water ice now frozen in place in Europa’s crust suggest they floated freely for a time. Credit: NASA/JPL-Caltech

Two: While recent discoveries have shown that many bodies in the solar system either have subsurface oceans now, or may have in the past, Europa is one of only two places where the ocean appears to be in contact with a rocky seafloor (the other being Saturn’s moon Enceladus). This rare circumstance makes Europa one of the highest priority targets in the search for present-day life beyond Earth.

On Earth, chemical interactions between life and lifeless rock in deep oceans and within the outer crust provide the energy needed to power and sustain microbial life. For all we know, deep sea volcanoes belch essential elements into the salty waters spawned by the constant flexing and heating of the moon as it orbits Jupiter every 85 hours.

 

This mosaic of images includes the most detailed view of the surface of Jupiter’s moon Europa obtained by NASA’s Galileo mission. This observation was taken with the sun relatively high in the sky, so most of the brightness variations are due to color differences in the surface material rather than shadows. Ridge tops, brightened by frost, contrast with darker valleys, perhaps due to small temperature variations allow frost to accumulate in slightly colder, higher-elevation locations. Credit: NASA/JPL-Caltech

The SDT was tasked with developing a life-detection strategy, a first for a NASA mission since the Mars Viking mission era more than four decades ago. The report makes recommendations on the number and type of science instruments that would be required to confirm if signs of life are present in samples collected from the icy moon’s surface.

The team also worked closely with engineers to design a system capable of landing on a surface about which very little is known. Given that Europa has no atmosphere, the team developed a concept that could deliver its science payload to the icy surface without the benefit of technologies like a heat shield or parachutes.

This artist’s rendering shows NASA’s Europa mission spacecraft, which is being developed for a launch sometime in the 2020s. The spacecraft would orbit around Jupiter in order to perform a detailed investigation of Europa before a follow-up landing mission. The probe could look for “biosignatures” or molecular signs of life, such as the byproducts of metabolism, transported from the moon’s ocean to its surface. Credit: NASA/JPL-Caltech

The concept lander is separate from the solar-powered Europa multiple flyby mission, now in development for launch in the early 2020s. The spacecraft will arrive at Jupiter after a multi-year journey, orbiting the gas giant every two weeks for a series of 45 close flybys of Europa. The multiple flyby mission will investigate Europa’s habitability by mapping its composition, determining the characteristics of the ocean and ice shell, and increasing our understanding of its geology. The mission also will lay the foundation for a future landing by performing detailed reconnaissance using its powerful cameras.

We can’t help but be excited by the prospects of life-seeking missions to Europa. Sometimes wonderful things come in small packages.

Europa’s Venting Global Ocean May Be Easier To Reach Than We Thought

Last week, on Tuesday, September 20th, NASA announced that they had made some interesting findings about Jupiter’s icy moon Europa. These were based on images taken by the Hubble Space Telescope, the details of which would be released on the following week. Needless to say, since then, the scientific community and general public have been waiting with baited breath.

Earlier today (September 26th) NASA put an end to the waiting and announced the Hubble findings during a NASA Live conference. According to the NASA panel, which was made up of members of the research team, this latest Europa-observing mission revealed evidence of plumes of saline water emanating from Europa’s surface. If true, this would mean that the moon’s subsurface ocean would be more accessible than previously thought.

Using Hubble’s Space Telescope Imaging Spectrograph (STIS) instrument, the team conducted observations of Jupiter and Europa in the ultra-violet spectrum over the course of 15 months. During that time, Europa passed in front of Jupiter (occulted the gas giant) on 10 separate occasions.

And on three of these occasions, the team saw what appeared to be plumes of water erupting from the surface. These plumes were estimated to be reaching up to 200 km (125 miles) from the southern region of Europa before (presumably) raining back onto the surface, depositing water ice and material from the interior.

The purpose of the observation was to examine Europa’s possible extended atmosphere (aka. exosphere). The method the team employed was similar to the one used to detect atmospheres around extra-solar planets. As William Sparks of the Space Telescope Science Institute (STScI) in Baltimore (and the team leader), explained in a NASA press release:

“The atmosphere of an extrasolar planet blocks some of the starlight that is behind it. If there is a thin atmosphere around Europa, it has the potential to block some of the light of Jupiter, and we could see it as a silhouette. And so we were looking for absorption features around the limb of Europa as it transited the smooth face of Jupiter.”

When they looked at Europa using this same technique, they noted that small patches on the surface were dark, indicating the absorption of UV light. This corresponded to previous work done by Lorenz Roth (of the Southwest Research Institute) and his team of researchers in 2012. At this time, they detected evidence of water vapor coming from Europa’s southern polar region.

Europa transit illustration. Europa orbits Jupiter every 3 and a half days, and on every orbit it passes in front of Jupiter, raising the possibility of plumes being seen as silhouettes absorbing the background light of Jupiter. Credits: A. Field (STScI)
Europa transit illustration. Europa orbits Jupiter every 3 and a half days, and on every orbit it passes in front of Jupiter, raising the possibility of plumes being seen as silhouettes absorbing the background light of Jupiter. Credits: A. Field (STScI)

As they indicated in a paper detailing their results – titled “Transient Water Vapor at Europa’s South Pole” – Roth’s team also relied on UV observations made using the Hubble telescope. Noting a statistically coincident amount of hydrogen and oxygen emissions, they concluded that this was the result of ejected water vapor being broken apart by Jupiter’s radiation (a process known as radiolysis).

Though their methods differed, Sparks and his research team also found evidence of these apparent water plumes, and in the same place no less. Based on the latest information from STIS, most of the apparent plumes are located in the moon’s southern polar region while another appears to be located in the equatorial region.

“When we calculate in a completely different way the amount of material that would be needed to create these absorption features, it’s pretty similar to what Roth and his team found,” Sparks said. “The estimates for the mass are similar, the estimates for the height of the plumes are similar. The latitude of two of the plume candidates we see corresponds to their earlier work.”

Another interesting conclusion to come from this and the 2012 study is the likelihood that these water plumes are intermittent. Basically, Europa is tidally-locked world, which means the same side is always being presented to us when it transits Jupiter. This occus once every 3.5 days, thus giving astronomers and planetary scientists plenty of viewing opportunities.

 This composite image shows suspected plumes of water vapor erupting at the 7 o’clock position off the limb of Jupiter’s moon Europa. The Hubble data were taken on January 26, 2014. Credit: Credits: NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center
This composite image shows suspected plumes of water vapor erupting at the 7 o’clock position off the limb of Jupiter’s moon Europa. The Hubble data were taken on January 26, 2014. Credit: Credits: NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center

But the fact that plumes have been observed at some points and not others would seem to indicate that they are periodic. In addition, Roth’s team attempted to spot one of the plume’s observed by Sparks and his colleagues a week after they reported it. However, they were unable to locate this supposed water source. As such, it would appear that the plumes, if they do exist, are short-lived.

These findings are immensely significant for two reasons. On the one hand, they are further evidence that a warm-water, saline ocean exists beneath Europa’s icy surface. On the other, they indicate that any future mission to Europa would be able to access this salt-water ocean with greater ease.

Ever since the Galileo spacecraft conducted a flyby of the Jovian moon, scientists have believed that an interior ocean is lying beneath Europa’s icy surface – one that has between two and three times as much water as all of Earth’s oceans combined. However, estimates of the ice’s thickness range from it being between 10 to 30 km (6–19 mi) thick – with a ductile “warm ice” layer that increases its total thickness to as much as 100 km (60 mi).

Knowing the water periodically reaches the surface through fissures in the ice would mean that any future mission (which would likely include a submarine) would not have to drill so deep. And considering that Europa’s interior ocean is considered to be one of our best bets for finding extra-terrestrial life, knowing that the ocean is accessible is certainly exciting news.

A comparison of 2014 transit and 2012 Europa aurora observations. The raw transit image, left, has dark fingers or patches of possible absorption in the same place that a different team (led by Lorenz Roth) found auroral emission from hydrogen and oxygen, the dissociation products of water. Credits: NASA, ESA, W. Sparks (left image) L. Roth (right image)
A comparison of 2014 transit and 2012 Europa aurora observations. Credits: NASA, ESA, W. Sparks (left image) L. Roth (right image)

And the news is certainly causing its fair share of excitement for the people who are currently developing NASA’s proposed Mission to Europa, which is scheduled to launch sometime in the 2020s. As Dr. Cynthia B. Phillips, a Staff Scientist and the Science Communications Lead for the Europa Project, told Universe Today via email:

“This new discovery, using Hubble Space Telescope data, is an intriguing data point that helps lend support to the idea that there are active plumes on Europa today. While not an absolute confirmation, the new Sparks et al. result, in combination with previous observations by Roth et al. (also using HST but with a different technique), is consistent with the presence of intermittent plumes ejecting water vapor from the Southern Hemisphere of Europa. Such observations are difficult to perform from Earth, however, even with Hubble, and thus these results remain inconclusive.

“Confirming the presence or absence of plumes on Europa, as well as investigating many other mysteries of this icy ocean world, will require a dedicated spacecraft in the Jupiter system.   NASA currently plans to send a multiple-flyby spacecraft to Europa, which would make many close passes by Europa in the next decade. The spacecraft’s powerful suite of scientific instruments will be able to study Europa’s surface and subsurface in unprecedented detail, and if plumes do exist, it will be able to observe them directly and even potentially measure their composition.  Until the Europa spacecraft is in place, however, Earth-based observations such as the new Hubble Space Telescope results will remain our best technique to observe Jupiter’s mysterious moon.”

Naturally, Sparks was clear that this latest information was not entirely conclusive. While he believes that the results were statistically significant, and that there were no indications of artifacts in the data, he also emphasized that observations conducted in the UV wavelength are tricky. Therefore, more evidence is needed before anything can be said definitively.

In the future, it is hoped that future observation will help to confirm the existence of water plumes, and how these could have helped create Europa’s “chaos terrain”. Future missions, like NASA’s James Webb Space Telescope (scheduled to launch in 2018) could help confirm plume activity by observing the moon in infrared wavelengths.

As Paul Hertz, the director of the Astrophysics Division at NASA Headquarters in Washington, said:

“Hubble’s unique capabilities enabled it to capture these plumes, once again demonstrating Hubble’s ability to make observations it was never designed to make. This observation opens up a world of possibilities, and we look forward to future missions — such as the James Webb Space Telescope — to follow up on this exciting discovery.”

Other team members include Britney Schmidt, an assistant professor at the School of Earth and Atmospheric Sciences at Georgia Institute of Technology in Atlanta; and Jennifer Wiseman, senior Hubble project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Their work will be published in the Sept. 29 issue of the Astrophysical Journal.

And be sure to enjoy this video by NASA about this exciting find:

Further Reading: NASA Live

Hubble’s Surprising Find On Europa To Be Announced By NASA Monday

Europa as imaged by the Galileo spacecraft. Europa is a prime target in the search for life because of its sub-surface ocean. Image: NASA/JPL-Caltech/SETI Institute

NASA will make a “surprising” announcement about Jupiter’s moon Europa on Monday, Sept. 26th, at 2:00 PM EDT. They haven’t said much, other than there is “surprising evidence of activity that may be related to the presence of a subsurface ocean on Europa.” Europa is a prime target for the search for life because of its subsurface ocean.

The new evidence is from a “unique Europa observing campaign” aimed at the icy moon. The Hubble Space Telescope captured the images in these new findings, so maybe we’ll be treated to some more of the beautiful images that we’re accustomed to seeing from the Hubble.

Images from NASA's Galileo spacecraft show the intricate detail of Europa's icy surface. Image: NASA/JPL-Caltech/ SETI Institute
Images from NASA’s Galileo spacecraft show the intricate detail of Europa’s icy surface. Image: NASA/JPL-Caltech/ SETI Institute

We always welcome beautiful images, of course. But the real interest in Europa lies in its suitability for harboring life. Europa has a frozen surface, but underneath that ice there is probably an ocean. The frozen surface is thought to be about 10 – 30 km thick, and the ocean may be about 100 km (62 miles) thick. That’s a lot of water, perhaps double what Earth has, and that water is probably salty.

Back in 2012, the Hubble captured evidence of plumes of water vapor escaping from Europa’s south pole. Hubble didn’t directly image the water vapor, but it “spectroscopically detected auroral emissions from oxygen and hydrogen” according to a NASA news release at the time.

This artist's illustration shows what plumes of water vapour might look like being ejected from Europa's south pole. Image: NASA, ESA, L. Roth (Southwest Research Institute, USA/University of Cologne, Germany) and M. Kornmesser.
This artist’s illustration shows what plumes of water vapour might look like being ejected from Europa’s south pole. Image: NASA, ESA, L. Roth (Southwest Research Institute, USA/University of Cologne, Germany) and M. Kornmesser.

There are other lines of evidence that support the existence of a sub-surface ocean on Europa. But there are a lot of questions. Will the frozen top layer be several tens of kilometres thick, or only a few hundred meters thick? Will the sub-surface ocean be warm, liquid water? Or will it be frozen too, but warmer than the surface ice and still convective?

Two models of the interior of Europa. Image: NASA/JPL.
Two models of the interior of Europa. Image: NASA/JPL.

Hopefully, new evidence from the Hubble will answer these questions definitively. Stay tuned to Monday’s teleconference to find out what NASA has to tell us.

These are the scientists who will be involved in the teleconference:

  • Paul Hertz, director of the Astrophysics Division at NASA Headquarters in Washington
  • William Sparks, astronomer with the Space Telescope Science Institute in Baltimore
  • Britney Schmidt, assistant professor at the School of Earth and Atmospheric Sciences at Georgia Institute of Technology in Atlanta
  • Jennifer Wiseman, senior Hubble project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland

The NASA website will stream audio from the teleconference.

More About Europa:

Europa Clipper Team Braces For Bad News

An artist's concept of the Europa mission. The multi-year mission would conduct fly-bys of Europa designed to protect it from the extreme environment there. Image: NASA/JPL-Caltech

Jupiter’s moon Europa is a juicy target for exploration. Beneath its surface of ice there’s a warm salty, ocean. Or potentially, at least. And if Earth is our guide, wherever you find a warm, salty, ocean, you find life. But finding it requires a dedicated, and unique, mission.

If each of the bodies in our Solar System weren’t so different from each other, we could just have one or two types of missions. Things would be much easier, but also much more boring. But Europa isn’t boring, and it won’t be easy to explore. Exploring it will require a complex, custom mission. That means expensive.

NASA’s proposed mission to Europa is called the Europa Clipper. It’s been in the works for a few years now. But as the mission takes shape, and as the science gets worked out, a parallel process of budget wrangling is also ongoing. And as reported by SpaceNews.com there could be bad news incoming for the first-ever mission to Europa.

Images from NASA's Galileo spacecraft show the intricate detail of Europa's icy surface. Image: NASA/JPL-Caltech/ SETI Institute
Images from NASA’s Galileo spacecraft show the intricate detail of Europa’s icy surface. Image: NASA/JPL-Caltech/ SETI Institute

At issue is next year’s funding for the Europa Clipper. Officials with NASA’s Outer Planets Assessment Group are looking for ways to economize and cut costs for Fiscal Year (FY) 2017, while still staying on track for a mission launch in 2022.

According to Bob Pappalardo, Europa Clipper’s project scientist at the Jet Propulsion Laboratory, funding will be squeezed in 2017. “There is this squeeze in FY17 that we have,” said Pappalardo. “We’re asking the instrument teams and various other aspects of the project, given that squeeze, what will it take in the out years to maintain that ’22 launch.”

As for the actual dollar amounts, there are different numbers floating around, and they don’t all jive with each other. In 2016, the Europa Mission received $175 million from Congress, but in the administration’s budget proposal for 2017, they only requested $49.6 million.

There’s clearly some uncertainty in these numbers, and that uncertainty is reflected in Congress, too. An FY 2017 House bill earmarks $260 million for the Europa mission. And the Senate has crafted a bill in support of the mission, but doesn’t allocate any funding for it. Neither the Senate nor the Congress has passed their bills.

This is not the first time that a mis-alignment has appeared between NASA and the different levels of government when it comes to funding. It’s pretty common. It’s also pretty common for the higher level of funding to prevail. But it’s odd that NASA’s requested amount is so low. NASA’s own low figure of $49.6 million is fuelling the perception that they themselves are losing interest in the Europa Clipper.

But SpaceNews.com is reporting that that is not the case. According to Curt Niebur, NASA’s program scientist for the Europa mission, “Everyone is aware of how supportive and generous Congress has been of this mission, and I’m happy to say that that support and encouragement is now shared by the administration, and by NASA as well. Everybody is on board the Europa Clipper and getting this mission to the launch pad as soon as our technical challenges and our budget will allow.”

What all this seems to mean is that the initial science and instrumentation for the mission will be maintained, but no additional capacity will be added. NASA is no longer considering things like free-flying probes to measure the plumes of water ice coming off the moon. According to Niebur, “The additional science value provided by these additions was not commensurate with the associated impact to resources, to accommodation, to cost. There just wasn’t enough science there to balance that out.”

The Europa Clipper will be a direct shot to Europa, without any gravity assist on the way. It will likely be powered by the Space Launch System. The main goal of the mission is to learn more about the icy moon’s potential habitability. There are tantalizing clues that it has an ocean about 100 km thick, kept warm by the gravity-tidal interactions with Jupiter, and possibly by radioactive decay in the rocky mantle. There’s also some evidence that the composition of the sub-surface ocean is similar to Earth’s.

Mars is a fascinating target, no doubt about it. But as far as harbouring life, Europa might be a better bet. Europa’s warm, salty ocean versus Mar’s dry, cold surface? A lot of resources have been spent studying Mars, and the Europa mission represents a shift in resources in that regard.

It’s unfortunate that a few tens of million dollars here or there can hamper our search for life beyond Earth. But the USA is a democracy, so that’s the way it is. These discrepancies and possible disputes between NASA and the different levels of government may seem disconcerting, but that’s the way these things get done.

At least we hope it is.

Sources: SpaceNews.com

Europa on Universe Today:

SpaceNews.com

Icy Hot: Europa’s Frozen Crust Could Be Warmer Than We Thought

All the worlds may be ours except Europa but that only makes the ice-covered moon of Jupiter all the more intriguing. Beneath Europa’s thin crust of ice lies a tantalizing global ocean of liquid water somewhere in the neighborhood of 100 kilometers deep—which adds up to more liquid water than is on the entire surface of the Earth. Liquid water plus a heat source(s) to keep it liquid plus the organic compounds necessary for life and…well, you know where the thought process naturally goes from there.

And now it turns out Europa may have even more of a heat source than we thought. Yes, a big component of Europa’s water-liquefying warmth comes from tidal stresses enacted by the massive gravity of Jupiter as well as from the other large Galilean moons. But exactly how much heat is created within the moon’s icy crust as it flexes has so far only been loosely estimated. Now, researchers from Brown University in Providence, RI and Columbia University in New York City have modeled how friction creates heat within ice under stress, and the results were surprising.

Continue reading “Icy Hot: Europa’s Frozen Crust Could Be Warmer Than We Thought”