Category: Europa

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A submersible probe that could possibly be used on Jupiter’s icy moon, Europa is taking the next step to test its capabilities. The Environmentally Non-Disturbing Under-ice Robotic Antarctic Explorer, also known as ENDURANCE, will swim untethered under ice, and collect data to create three-dimensional maps of underwater environments. The probe also will take samples of microbial life. Earlier this year, it operated successfully in a 25 meter frozen lake in Wisconsin, USA. Now it will plunge under a permanently ice covered lake in Antarctica that is 40 meters deep. ENDURANCE isn’t like the Mars Rovers or other remote-operated probes. Once deployed, it’s on its own to systematically explore, take water samples, and find its way back. “It will have to think on its own,” said Peter Doran, an Earth scientist at the University of Illinois in Chicago.

In the February 2008 test, ENDURANCE successfully found its way around the bottom of the lake and back to the hole that drilled in the ice to get the probe in and out of the lake. It also demonstrated that its electronics functioned perfectly well in cold water.

At Lake Bonney in Antarctica, ENDURANCE will not only map the lake and explore its biology, but also take a close look at the base of a feature called Blood Falls, where reddish, iron-containing salts spill out of the face of a glacier at the lake’s upper end.

If all goes well the next test would have the probe or an improved version descend through 3.5 km of ice to one of the world’s largest, deepest and most mysterious lakes, Lake Vostok, also in Antarctica.
But even that pales in comparison to what a probe might encounter at Europa. Scientists believe that Europa’s ocean could be up to 100 kilometers deep, under 6 kilometers of ice.

Hot water drills will bore a hole for ENDURANCE to enter the water in Antarctica. If all goes well, the probe will be tested again in 2009.

But many hurdles remain before an underwater vehicle could possibly head to Europa. Presently, Endurance is too massive to send on interplanetary travel. Engineers will also have to come up with a way to drill through Europa’s icy crust and lower the sub safely through the ice.

But many scientists feel that an orbiting spacecraft would be the best way to study Europa, before sending an underwater probe. The Jet Propulsion Laboratory is currently working on a concept called the Europa Explorer which would deliver a low orbit spacecraft to determine the presence (or absence) of a liquid water ocean under Europa’s ice surface. It would also map the surface and subsurface for future exploration.

Source: COSMOS

Curved features on Jupiter’s moon Europa may indicate that its poles have wandered by almost 90°, a new study reports. Researchers believe the drastic shift in Europa’s rotational axis was likely a result of the build-up of thick ice at the poles. “A spinning body is most stable with its mass farthest from its spin axis,” says Isamu Matsuyama of the Carnegie Institution’s Department of Terrestrial Magnetism. “On Europa, variations in the thickness of its outer shell caused a mass imbalance, so the rotation axis reoriented to a new stable state” An extreme shift like this also suggests the existence of an internal liquid ocean beneath the icy crust.

The research team, led by Dr. Paul Schenk of the Lunar and Planetary Institute and joined by Matsuyama and Dr. Francis Nimmo of the University of California, Santa Cruz, used images from the Voyager, Galileo, and New Horizons spacecraft to map several large arc-shaped depressions that extend more than 500 kilometers across Europa’s surface. With a radius of about 1500 kilometers, Europa is slightly smaller than the Earth’s moon.

By comparing the pattern of the depressions with fractures that would result from stresses caused by a shift in Europa’s rotational axis, the researchers determined that the axis had shifted by approximately 80°. The previous axis of rotation is now located about 10° from the present equator.

Such a change is called “true polar wander” as opposed to apparent polar wander caused by plate tectonics. There is evidence for true polar wander on Earth, and also on Mars and on Saturn’s moon Enceladus. “Our study adds Europa to this list,” says Matsuyama. “It suggests that planetary bodies might be more prone to reorientation than we thought.”

The study also has implications for liquid water inside Europa. Many scientists believe Europa has an extensive subsurface ocean based on spacecraft photos showing a fractured, icy surface. The ocean beneath the crust would be kept liquid by heat generated by tidal forces from Jupiter’s gravity. The presence of heat and water may make life possible, even though the subsurface ocean is cut off from solar energy.

“The large reorientation on Europa required to explain the circular depressions implies that its outer ice shell is decoupled from the core by a liquid layer,” says Matsuyama. “Therefore, our study provides an independent test for the presence of an interior liquid layer.”

Original News Source: EurekAlert

Nick had an article last week about a new technique that might help scientists figure out just how deep the oceans on Europa are. Deep oceans with a thin crust might give a rover, or a submarine, a fighting chance to get down to that precious H2O, and sample it for evidence of life. Researchers are seriously discussing the benefits of exploring Europa at the annual meeting of the American Geophysical Union in San Francisco.

According to William McKinnon, a professor of Earth and Planetary Sciences at Washington University in St. Louis, Mo, “We’ve learned a lot about Europa in the past few years.

“Before we were almost sure that there was an ocean, but now the scientific community has come to a consensus that there most certainly is an ocean. We’re ready to take the next step and explore that ocean and the ice shell that overlays it. We have a number of new discoveries and techniques that can help us do that.”

What advances have been made?

There’s the research we talked about; how detailed observations of the Moon’s flexing under Jupiter’s intense gravity, as well as the magnetic variations can tell just how deep the ocean goes.

And new radar sounding techniques have been developed for other spacecraft that would be very useful at Europa. The high-resolution radar system installed on the Mars Reconnaissance Orbiter would be able to peer right through an ice shell on Europa, and give researchers a cross section of the ice. It would be able to locate liquid water under and within the shell, and put the controversy to rest forever.

Engineers are also working on future explorers, such as a project called Endurance, developed by Peter Doran, associate professor of Earth and Environmental Sciences, University of Illinois at Chicago and Stone Aerospace. They’ll be testing an exploration vehicle in Wisconsin in February 2008, and then in Antarctica.

This robotic explorer will be able to create three-dimensional maps of the subsurface lakes in Antarctica and even map out the biochemistry in the water. If there’s life there, Endurance will find it.

Obviously, sending a probe like this to Europa is a long, long way off. But people are chipping away at the problem on both ends. Scientists are making the case that Europa is one of the most enticing scientific targets in the Solar System. And engineers are working out the technologies that could actually make the discoveries.

The future for exploration on Europa is looking brighter every day.

Original Source: University of Texas at Austin News Release

How do you determine the thickness of an ocean that you can’t see, let alone know how salty it is? Europa, the sixth satellite from Jupiter, is thought to have an ocean of liquid water underneath its icy surface. We know this because of its remarkably uncratered surface and the way its magnetic field reacts with that of Jupiter. New results that take into consideration Europa’s interaction with the plasma surrounding Jupiter – in addition to the magnetic field – give us a better picture of the ocean’s thickness and composition. This will help future robotic explorers know how deep they need to tunnel to reach the oceans underneath.

“We know from gravity measurements made by Galileo that Europa is a differentiated body. The most plausible models of Europa’s interior have an H2O-ice layer of thickness 80-170km. However, the gravity measurements tell us nothing about the state of this layer (solid or liquid),” said Dr. Nico Schilling of the Institut für Geophysik und Meteorologie in Köln, Germany.

The water in Europa’s ocean – just like the water in our own ocean – is a good conductor of electricity. When a conductor passes through a magnetic field, electricity is produced, and this electricity has an effect on the magnetic field itself. It’s just like what happens inside an electric generator. This process is called electromagnetic induction, and the intensity of the induction gives a lot of information about the materials involved in the process.

But Europa doesn’t only interact with the magnetic field coming from Jupiter, however; it also has electromagnetic interactions with the plasma surrounding Jupiter, called the magnetospheric plasma. This same thing happens on Earth in a way that is very familiar: Earth has a magnetosphere, and when plasma coming from the Sun interacts with our magnetosphere we see the beautiful Aurora Borealis phenomenon.

This process, happening intermittently as Europa orbits Jupiter, has an effect on the induction field of the subsurface ocean of the moon. By combining these measurements with the previous measurements of the interaction between Europa and Jupiter’s magnetic field, the researchers were able to get a better picture of just how thick and how conductive Europa’s ocean is. Their results were published in a paper titled, Time-varying interaction of Europa with the jovian magnetosphere: Constraints on the conductivity of Europa’s subsurface ocean, which appears in the August 2007 edition of the journal Icarus.

The researchers compared their models of Europa’s electromagnetic induction with the results of Galileo’s magnetic field measurements, and found that the total conductivity of the ocean was about 50,000 Siemens (a measure of electrical conductivity). This is much higher than previous results, which placed the conductivity at 15000 Siemens.

Depending on the composition of the ocean, though, the thickness could be between 25 and 100km, which is also thicker than the previously estimated lower limit of 5km. The less conductive the ocean is, the thicker it must be to account for the measured conductivity, and this depends on the quantity and type of salt found in the ocean, which still remains unknown.

Taking into account the interactions with the magnetospheric plasma are important when studying the composition of planets and moons.

Dr. Schilling said, “The plasma interaction effects the magnetic field measurements, but not e.g. the gravity measurements. So in every case in the Jupiter system, where magnetic field measurements were used to get some informations from the interiors of the moons, the plasma interaction has to be considered. An example is for instance Io, where the first flybys suggested that Io may have an internal dynamo field. It turned out that the measured magnetic field perturbation was not an internal field but was created by the plasma interaction.”

Europa and Io, though, are not the only place where magnetic fields and plasma interactions can tell us about the nature of a planet’s interior; this same method was also used to detect the geysers of Enceladus, one of Saturn’s moons.

“The first hints of an active south polar region came from the magnetic field measurements and the simulations of the plasma interaction, before Cassini actually saw the geysers,” Dr. Schilling said.

With the discovery of entire ecosystems at the bottom of oceans here on Earth – ecosystems entirely cut off from sunlight – the discovery of oceans on Europa gives scientists hope that there could be life there. And this new discovery helps researchers understand what kind of ocean they could be dealing with.

Now, we just have to tunnel down through the shell of ice and look for ourselves.

Source: Icarus