Shallow Pockets of Water Under the ice on Europa Could Bring Life Close to its Surface

This artist’s conception shows how double ridges on the surface of Jupiter’s moon Europa may form over shallow, refreezing water pockets within the ice shell. This mechanism is based on the study of an analogous double ridge feature found on Earth’s Greenland Ice Sheet. (Image credit: Justice Blaine Wainwright)

Beneath the surface of Jupiter’s icy moon Europa, there’s an ocean up to 100 km (62 mi) deep that has two to three times the volume of every ocean on Earth combined. Even more exciting is how this ocean is subject to hydrothermal activity, which means it may have all the necessary ingredients for life. Because of this, Europa is considered one of the most likely places for extraterrestrial life (beyond Mars). Hence, mission planners and astrobiologists are eager to send a mission there to study it closer.

Unfortunately, Europa’s icy surface makes the possibility of sampling this ocean rather difficult. According to the two predominant models for Europa’s structure, the ice sheet could be a few hundred meters to several dozen kilometers thick. Luckily, new research by a team from Stanford University has shown that Europa’s icy shell may have an abundance of water pockets inside, as indicated by features on the surface that look remarkably like icy ridges here on Earth.

Continue reading “Shallow Pockets of Water Under the ice on Europa Could Bring Life Close to its Surface”

Europa has Water in its Atmosphere

Observations by the NASA/ESA Hubble Space Telescope recently revealed water vapour in the atmosphere of Ganymede, one of Jupiter’s moons. A new analysis of archival images and spectra has now revealed that water vapour is also present in the atmosphere of Jupter’s icy moon Europa. The analysis found that a water vapour atmosphere is present only on one hemisphere of the moon. This result advances our understanding of the atmospheric structure of icy moons, and helps lay the groundwork for upcoming science missions which will explore Jupiter’s icy moons.

Since the Voyager probes passed through the Jupiter system in 1979, scientists have been intrigued and mystified by its moon Europa. Once the images these probes acquired of the moon’s icy surface returned to Earth, scientists began to speculate about the possibility of a subsurface ocean. Since then, the detection of plume activity and other lines of evidence have bolstered this theory and fed speculation that there could be life beneath Europa’s icy surface.

According to new research, another critical piece of evidence of Europa’s watery nature has at least been confirmed. Using a similar technique that confirmed the presence of atmospheric water vapor in Jupiter’s moon Ganymede, Lorenz Roth of the KTH Royal Institute of Technology confirmed that Europa has water vapor in its atmosphere. This discovery could lead to a greater understanding of Europa’s atmosphere and surface environment, informing missions headed there in the near future.

Continue reading “Europa has Water in its Atmosphere”

Beyond “Fermi’s Paradox” XIII: What is the “Ocean Worlds” Hypothesis?

Credit: NASA/JPL

Welcome back to our Fermi Paradox series, where we take a look at possible resolutions to Enrico Fermi’s famous question, “Where Is Everybody?” Today, we examine the possibility that the reason for the Great Silence is that most life out there exists in warm water oceans under sheets of ice!

In 1950, Italian-American physicist Enrico Fermi sat down to lunch with some of his colleagues at the Los Alamos National Laboratory, where he had worked five years prior as part of the Manhattan Project. According to various accounts, the conversation turned to aliens and the recent spate of UFOs. Into this, Fermi issued a statement that would go down in the annals of history: “Where is everybody?

This became the basis of the Fermi Paradox, which refers to the disparity between high probability estimates for the existence of extraterrestrial intelligence (ETI) and the apparent lack of evidence. Since Fermi’s time, there have been several proposed resolutions to his question, which include the possibility that Oceans Worlds (and not rocky planets) might be the best candidates for finding life.

Continue reading “Beyond “Fermi’s Paradox” XIII: What is the “Ocean Worlds” Hypothesis?”

Europa’s Nightside Glows in the Dark

This illustration of Jupiter's moon Europa shows how the icy surface may glow on its nightside, the side facing away from the Sun. Variations in the glow and the color of the glow itself could reveal information about the composition of ice on Europa's surface. Credit: NASA/JPL-Caltech

In a few years, NASA will be sending a spacecraft to explore Jupiter’s icy moon Europa. Known as the Europa Clipper mission, this orbiter will examine the surface more closely to search for plume activity and evidence of biosignatures. Such a find could answer the burning question of whether or not there is life within this moon, which is something scientists have speculated about since the 1970s.

In anticipation of this mission, scientists continue to anticipate what it will find once it gets there. For instance, scientists from NASA’s Jet Propulsion Laboratory recently conducted a study that showed how Europa might glow in the dark. This could be the result of Europa constantly being pummeled with high-energy radiation from Jupiter’s magnetic field, the study of which could tell scientists more about the composition of Europa’s ice.

Continue reading “Europa’s Nightside Glows in the Dark”

Planets With Large Oceans are Probably Common in the Milky Way

Credit: NASA/JPL

Within our Solar Systems, there are several moons where astronomers believe life could be found. This includes Ceres, Callisto, Europa, Ganymede, Enceladus, Titan, and maybe Dione, Mimas, Triton, and the dwarf planet Pluto. These “ocean worlds” are believed to have abundant liquid water in their interiors, as well as organic molecules and tidal heating – the basic ingredients for life.

Which raises the all-important question: are similar moons to be found in other star systems? This is the question NASA planetary scientist Dr. Lynnae C. Quick and her team from NASA’s Goddard Space Flight Center sought to address. In a recent study, Quick and her colleagues examined a sample of exoplanet systems and found that ocean worlds are likely to be very common in our galaxy.

Continue reading “Planets With Large Oceans are Probably Common in the Milky Way”

Europe’s Mission to Jupiter’s Moons Just Got its First Instrument

Southwest Research Institute’s Norm Pelletier prepares the Ultraviolet Spectrograph (UVS) for delivery and integration onto the European Space Agency’s JUICE spacecraft. As part of a 10-instrument payload to study Jupiter and its large moons, UVS will measure ultraviolet spectra that scientists will use to study the composition and structure of the atmospheres of these bodies and how they interact with Jupiter’s massive magnetosphere. Credit: SwRI

The space agencies of the world have some truly ambitious plans in mind for the coming decade. Alongside missions that will search for evidence for past (and maybe present) life on Mars, next-generation space telescopes, and the “return to the Moon”, there are missions will which will explore Jupiter’s moons for signs of extra-terrestrial life. These include the ESA’s JUpiter Icy Moon Explorer (JUICE), which will launch in 2022.

As part of the agency’s Cosmic Vision 2015-2025 program, this spacecraft will conduct detailed observations of Jupiter and three of its large moons – Ganymede, Callisto, and Europa – to see if they could indeed harbor life in their interiors. Late last month (Feb. 25th), the first instrument that will fly aboard JUICE and aid in these efforts was delivered and began the process of integration with the spacecraft.

Continue reading “Europe’s Mission to Jupiter’s Moons Just Got its First Instrument”

NASA Wants to Send a Low-Cost Mission to Explore Neptune’s Moon Triton

Global Color Mosaic of Triton, taken by Voyager 2 in 1989. Credit: NASA/JPL/USGS

In the coming years, NASA has some bold plans to build on the success of the New Horizons mission. Not only did this spacecraft make history by conducting the first-ever flyby of Pluto in 2015, it has since followed up on that by making the first encounter in history with a Kuiper Belt Object (KBO) – 2014 MU69 (aka. Ultima Thule).

Given the wealth of data and stunning images that resulted from these events (which NASA scientists are still processing), other similarly-ambitious missions to explore the outer Solar System are being considered. For example, there is the proposal for the Trident spacecraft, a Discovery-class mission that would reveal things about Neptune’s largest moon, Triton.

Continue reading “NASA Wants to Send a Low-Cost Mission to Explore Neptune’s Moon Triton”

ARCHIMEDES: Digging into the ice on Europa with lasers

The fascinating surface of Jupiter’s icy moon Europa looms large in this newly-reprocessed color view, made from images taken by NASA's Galileo spacecraft in the late 1990s. This is the color view of Europa from Galileo that shows the largest portion of the moon's surface at the highest resolution. Credits: NASA/JPL-Caltech/SETI Institute

Ever since the Pioneer and Voyager probes passed through the Jovian system in the 1970s, NASA and other space agencies have dreamed of one-day sending a mission to Europa. Beyond Earth, it is considered one of the most promising candidates for finding life, which could exist in the subsurface ocean that lies beneath the moon’s icy crust.

One of these concepts is known as the Cool High Impact Method for Exploring Down into Europan Subsurface (ARCHIMEDES), a proposed direct-laser penetrator that will use a laser light carried by an optical fiber tether to penetrate Europa’s icy crust. This mission could provide future missions with access to the ocean that exists beneath Europa’s surface and enable the search for life there.

Continue reading “ARCHIMEDES: Digging into the ice on Europa with lasers”

Life on Europa Would be Protected by Just a Few Centimeters of Ice

Radiation from Jupiter can destroy molecules on Europa's surface. Material from Europa's ocean that ends up on the surface will be bombarded by radiation, possibly destroying any biosignatures, or chemical signs that could imply the presence of life. Credit: NASA/JPL-Caltech

Ever since the Galileo probe provided compelling evidence for the existence of a global ocean beneath the surface of Europa in the 1990s, scientists have wondered when we might be able to send another mission to this icy moon and search for possible signs of life. Most of these mission concepts call for an orbiter or lander than will study Europa’s surface, searching the icy sheet for signs of biosignatures turned up from the interior.

Unfortunately, Europa’s surface is constantly bombarded by radiation, which could alter or destroy material transported to the surface. Using data from the Galileo and Voyager 1 spacecraft, a team of scientists recently produced a map that shows how radiation varies across Europa’s surface. By following this map, future missions like NASA’s Europa Clipper will be able to find the spots where biosignatures are most likely to still exist.

As many missions have revealed by studying Europa’s surface, the moon experiences periodic exchanges between the interior and the surface. If there is life in its interior ocean, then biological material could theoretically be brought to the surface where it could be studied. Since radiation from Jupiter’s magnetic field would destroy this material, knowing where it is most intense, how deep it goes, and how it could affect the interior are all important questions.

Artist’s impression of water bubbling up from Europa’s interior ocean and breaching the surface ice. Credit: NASA/JPL-Caltech

As Tom Nordheim, a research scientist at NASA’s Jet Propulsion Laboratory, explained in a recent NASA press release:

“If we want to understand what’s going on at the surface of Europa and how that links to the ocean underneath, we need to understand the radiation. When we examine materials that have come up from the subsurface, what are we looking at? Does this tell us what is in the ocean, or is this what happened to the materials after they have been radiated?”

To address these question, Nordheim and his colleagues examined data from Galileo‘s flybys of Europa and electron measurements from NASA’s Voyager 1 spacecraft. After looking closely at the electrons blasting the moon’s surface, Nordheim and his team found that the radiation doses vary by location. The harshest radiation is concentrated in zones around the equator, and the radiation lessens closer to the poles.

The study which describes their findings recently appeared in the scientific journal Nature under the title “Preservation of potential biosignatures in the shallow subsurface of Europa“. The study was led by Nordheim and was co-authored by Kevin Hand (also with the JPL) and Chris Paranicas from the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland.

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

“This is the first prediction of radiation levels at each point on Europa’s surface and is important information for future Europa missions,” said Paranicas. Now that scientists know where to find regions least altered by radiation, they will be able to designate areas of study for the Europa Clipper, a JPL-led mission that is expected to launch as early as 2022.

For the sake of their study, Nordheim and his team went beyond a conventional two-dimensional map to build 3D models that examined how far below the surface the radiation penetrates. To test how deep organic material would have to be buried in order to survive, Nordheim and his team tested the effect of radiation on amino acids (the basic building blocks for proteins) to figure out how Europa’s exposure to radiation would affect potential biosignatures.

The results indicate how deep scientists will need to dig or drill during a potential future Europa lander mission in order to find any biosignatures that might be preserved. In the highest-radiation zones around the equator, the depth at which biosignatures could be found ranged from 10 to 20 cm (4 to 8 inches). At the middle- and high-latitudes, closer to the poles, the depths decrease to about 1 cm (0.4 inches). As Hand indicated:

“The radiation that bombards Europa’s surface leaves a fingerprint. If we know what that fingerprint looks like, we can better understand the nature of any organics and possible biosignatures that might be detected with future missions, be they spacecraft that fly by or land on Europa.”

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

When the Europa Clipper mission reaches the Jovian system, the spacecraft will orbit Jupiter and conducting about 45 close flybys of Europa. It’s advanced suite of scientific instruments will include cameras, spectrometers, plasma and radar instruments which will investigate the composition of the moon’s surface, its ocean, and material that has been ejected from the surface.

“Europa Clipper’s mission team is examining possible orbit paths, and proposed routes pass over many regions of Europa that experience lower levels of radiation,” Hand said. “That’s good news for looking at potentially fresh ocean material that has not been heavily modified by the fingerprint of radiation.”

With this new radiation map, the mission team will be able to narrow the range of possible research sites. This, in turn, will increase the likelihood that the orbiter mission will be able to settle the decades-old mystery of whether or not there is life in the Jovian system.

Further Reading: NASA, Nature

NASA Simulation Shows How Europa’s “Fossil Ocean” Rises to the Surface Over Time

Based on new evidence from Jupiter's moon Europa, 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. The new findings propose answers to questions that have been debated since the days of NASA's Voyager and Galileo missions. This illustration of Europa (foreground), Jupiter (right) and Io (middle) is an artist's concept. Credit: NASA/JPL-Caltech

In the 1970s, the Jupiter system was explored by a succession of robotic missions, beginning with the Pioneer 10 and 11 missions in 1972/73 and the Voyager 1 and 2 missions in 1979. In addition to other scientific objectives, these missions also captured images of Europa’s icy surface features, which gave rise to the theory that the moon had an interior ocean that could possibly harbor life.

Since then, astronomers have also found indications that there are regular exchanges between this interior ocean and the surface, which includes evidence of plume activity captured by the Hubble Space Telescope. And recently, a team of NASA scientists studied the strange features on Europa’s surface to create models that show how the interior ocean exchanges material with the surface over time.

The study, which recently appeared in the the Geophysical Research Letters under the title “Band Formation and Ocean-Surface Interaction on Europa and Ganymede“, was conducted by Samuel M. Howell and Robert T. Pappalardo – two researchers from the NASA Jet Propulsion Laboratory. For their study, the team examined both Ganymede and Europa to see what the moons surface features indicated about how they changed over time.

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

Using the same two-dimensional numerical models that scientists have used to solve mysteries about motion in the Earth’s crust, the team focused on the linear features known as “bands” and “groove lanes” on Europa and Ganymede. The features have long been suspected to be tectonic in nature, where fresh deposits of ocean water have risen to the surface and become frozen over previously-deposited layers.

However, the connection between this band-forming processes and exchanges between the ocean and the surface has remained elusive until now. To address this, the team used their 2-D numerical models to simulate ice shell faulting and convection.Their simulations also produced a beautiful animation that tracked the movement of “fossil” ocean material, which rises from the depths, freezes into the base of the icy surface, and deforms it over time.

Whereas the white layer at the top is the surface crust of Europa, the colored band in the middle (orange and yellow) represents the stronger sections of the ice sheet. Over time, gravitational interactions with Jupiter cause the ice shell to deform, pulling the top layer of ice apart and creating faults in the upper ice. At the bottom is the softer ice (teal and blue), which begins to churn as the upper layers pull apart.

This causes water from Europa’s interior ocean, which is in contact with the softer lower layers of the icy shell (represented by white dots), to mix with the ice and slowly be transported to the surface. As they explain in their paper, the process where this “fossil” ocean material becomes trapped in Europa’s ice shell and slowly rises to the surface can take hundreds of thousands of years or more.

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

As they state in their study:

“We find that distinct band types form within a spectrum of extensional terrains correlated to lithosphere strength, governed by lithosphere thickness and cohesion. Furthermore, we find that smooth bands formed in weak lithosphere promote exposure of fossil ocean material at the surface.”

In this respect, once this fossil material reaches the surface, it acts as a sort of geological record, showing how the ocean was millions of years ago and not as it is today. This is certainly significant when it comes to future missions to Europa, such as NASA’s Europa Clipper mission. This spacecraft, which is expected to launch sometime in the 2020s, will be the first to study Europa exclusively.

In addition to studying the composition of Europa’s surface (which will tell us more about the composition of the ocean), the spacecraft will be studying surface features for signs of current geological activity. On top of that, the mission intends to look for key compounds in the surface ice that would indicate the possible presence of life in the interior (i.e. biosignatures).

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

If what this latest study indicates is true, then the ice and compounds the Europa Clipper will be examining will essentially be “fossils” from hundreds of thousands or even millions of years ago. In short, any biomarkers the spacecraft detects – i.e. signs of potential life – will essentially be dated. However, this need not deter us from sending missions to Europa, for even evidence of past life would be groundbreaking, and a good indication that life still exists there today.

If anything, it makes the case for a lander that can explore Europa’s plumes, or perhaps even a Europa submarine (cryobot), all the more necessary! If there is life beneath Europa’s icy surface, we are determined to find it – provided we don’t contaminate it in the process!

Further Reading: NASA, Geophysical Research Letters