Marshall Space Flight Center Press Release

March 6, 1998

Clues to possible life on Europa may lie buried in Antarctic ice

March 5, 1998: More than a century ago, science fiction pioneer Jules Verne wrote about people swept "Off on a Comet" and into space where they lived more or less happily ever after.

Verne's 1877 book (also published as "Hector Servadac") was a bit fanciful, but it had an element of truth: life may have hitchhiked across the solar system. The proof may be found at the ends of the Earth. This week, American and Russian scientists are examining deep ice from the Antarctic and hoping to find clues that fungi, bacteria, and even diatoms could survive conditions in icy solar system bodies. This would help make the South Pole one of the first destinations for the growing field of astrobiology.

"It's possible to say that ancient impacts of asteroids on the [Antarctica] Earth could have ejected soil, rocks, and seawater containing terrestrial microorganisms into space, and that they may have made it to other places in the solar system," explained Richard Hoover at NASA's Marshall Space Flight Center. Hoover is an X-ray astronomer who is also is internationally known for his work on diatoms and a firm believer that living microorganisms locked in ice have a chance of remaining viable for long periods in outer space.

The debate over whether the Antarctic Allan Hills meteorites brought life from Mars (or were contaminated by life on Earth) is the best known case. Hoover said that other evidence abounds, including asteroids striking the Earth or Mars and blasting materials into space, the survival of streptococcus bacteria on the Surveyor 3 moon lander, and the survival of microorganisms inside Antarctic ice.

The possibilities expanded this week when NASA released new images and data that Europa, one of Jupiter's larger moons, slush and perhaps liquid water near the surface. That raises the intriguing possibility that Europa may harbor life.

Discoveries on the Earth over the last few years show that life thrives or can be preserved in a range of "hostile" conditions, from volcanic vents deep in ocean trenches, to ice more than 400,000 years old, to Siberian permafrost more than 5 million years old.

This week, Hoover and Dr. S. S. Abyzov of Russia's Institute of Microbiology of the Russian Academy of Sciences in Moscow are examining ancient ice drilled at Russia's Vostok (East) Station about 1,000 km (1,600 mi) from the South Pole. Eventually, they hope to examine water taken from inside a lake - liquid, not ice - discovered under Vostok Station in 1996.

The first samples being examined are from 386 meters (1,266 ft) down; the deepest in this set is from 1,249 meters (4,097 ft). Samples from as deep as 3,610 meters (11,840 ft) are on their way from Vostok to the Institute of Microbiology. Abyzov says that portions will be brought to Marshall later this year.

Russian scientists have been drilling at Vostok since 1974. In 1996, seismic and other tools revealed the lake's presence in 1996. Lake Vostok is overlaid by about 3,710 meters (12,169 ft) of ice and may be 500,000 to 1 million years old. Since the discovery, drilling has gone slowly while procedures are worked out to keep it pristine. No one has seen or sampled the lake - the deepest ice sample is from 100 meters (328 feet) above the liquid surface - nor is anyone sure why it is liquid, hence the scientific curiosity. (Check below for links to stories about Lake Vostok.)

While Lake Vostok holds clues about life on Earth, it also is a good model for conditions on Europa (the image links to the latest news from Europa). The lake is about 48 by 224 km (30 by 140 mi) in size - about the size of Lake Ontario - and 484 meters (1,600 ft) deep. Recent data indicate that it has about 50 meters (165 ft) of sediment at the bottom.

"Recent research [shows] that extremely severe conditions of cosmic environments do not exclude the possibility that microorganisms may exist in anabiotic states at high altitudes in interplanetary space," Abyzov wrote in a recent paper. The only way to resolve the question is to use the Antarctic as a model for conditions in comets, the Martian ice caps, and other icy moons orbiting Jupiter and Saturn.

At Vostok station in 1975, Abyzov discovered bacteria, fungi, diatoms, and other microorganisms which were blown to Antarctica by winds from lower latitudes. The numbers of the organisms at different depths, and thus different ages of the ice, change with major climate changes on the Earth. Thus, the ice also serves as a time capsule, preserving specimens of life as far back as 500,000 years. This offers the potential for studying how genetic material changes over the centuries.

Abyzov brought his samples to Marshall to use the Environmental Scanning Electron Microscope, or ESEM, a relatively new tool that Marshall uses to analyze how materials fail and break. It was originally designed to analyze biological specimens in their natural environment, without coating them in gold to make them reflective. And that's ideal for observing whatever is in the ice. It also uses an X-ray scan to analyze the elements in a target, an important step in determining whether an object is organic.

The ice specimens will be analyzed at Marshall over the next week, then Abyzov will go to the Jet Propulsion Laboratory to work with another colleague with different analytical tools. Check back in a few days for a follow-up story on what the ESEM finds.

The Brown University News Bureau

March 2, 1998

DETAILED IMAGES FROM JUPITER MOON EUROPA POINT TO SLUSH BELOW SURFACE

The latest, most detailed pictures of the Jupiter moon Europa lend more support to the theory that slush or even liquid water lurks beneath the moon's surface. Those pictures were presented and discussed by scientists from Brown University and NASA during a press briefing today on the Brown campus.

PROVIDENCE, R.I. -- The most detailed images ever taken of the Jupiter moon Europa show more evidence for slush beneath the bright moon's icy surface, say planetary scientists from Brown University and NASA who have analyzed data recently transmitted from the Galileo spacecraft.

Slightly smaller than Earth's moon but many times brighter, Europa's icy surface has intrigued scientists ever since the Voyager spacecraft missions flew through the Jupiter system in 1979. At -260° F, the moon's surface temperature could deep-freeze an ocean over several million years, but some scientists are beginning to think that warmth from a tidal tug of war with Jupiter and neighboring moons could be keeping large parts of Europa's ocean liquid.

The latest images released today were taken in December 1997 by the Galileo spacecraft and just received on Earth. The new images provide three key pieces of evidence showing that Europa may be slushy just beneath the icy crust and possibly even warmer at greater depths. The evidence includes a strangely shallow impact crater, chunky textured surfaces like icebergs, and gaps where new icy crust seems to have formed between continent-sized plates of ice.

Some of the new images focus on the shallow center of the impact crater known as Pwyll. Impact rays and debris scattered over a large part of the moon show that a meteorite slammed into Europa relatively recently, about 10-100 million years ago. The darker debris around the crater suggests the impact excavated deeply buried material. But the crater's shallow basin and high set of mountain peaks may mean that subsurface ice was warm enough to collapse and fill in the deep hole, says Brown graduate student Geoffrey Collins, a member of the Galileo research team.

A subsurface ocean warm enough to be slushy also may explain the origins of an area littered with fractured and rotated blocks of crust the size of several city blocks, called "chaos" terrain. The new images show rough and swirly material between the fractured chunks, which may have been suspended in slush that froze at the very low surface temperatures, says Robert Pappalardo, a postdoctoral research scientist at Brown and a member of the Galileo research team.

On a larger scale, large plates of ice seem to be sliding over a warm interior on Europa, much like Earth's continental plates move around on our planet's partly molten interior.

The new images of Europa show that the darker wedge-shaped gaps between the plates of ice have many similarities to new crust formed at mid-ocean ridges on the Earth's sea floor, says Brown graduate student Louise Prockter, a member of the Galileo research team who has studied high-resolution sonar images of the Mid-Atlantic Ridge and has visited the Pacific Ocean floor in the research submersible vehicle Alvin. The new crust welling up between the separating plates on Europa was likely initially slushy ice or possibly liquid water that has frozen and fractured, Prockter says.

"Together, the evidence supports the hypothesis that in Europa's most recent history, liquid or at least partially liquid water existed at shallow depths below the surface of Europa in several different places," says James Head, Brown University professor of geological sciences and a group leader of the Galileo research team.

"The combination of interior heat, liquid water, and infall of organic material from comets and meteorites means that Europa has the key ingredients for life," Head says. "Europa, like Mars and the Saturn moon Titan, is a laboratory for the study of conditions that might have led to the formation of life in the solar system."

Images are available at http://www.jpl.nasa.gov/galileo and http://photojournal.jpl.nasa.gov.



BACKGROUND ON EUROPA DATA FROM THE GALILEO MISSION TO JUPITER

At today's press briefing, Brown and NASA scientists will show the most detailed images ever seen of the Jupiter moon Europa. Recently transmitted from the Galileo spacecraft, the images provide three key pieces of evidence supporting the idea that water may lurk beneath Europa's surface. (See also news advisory.)

Background

Water or ice? Liquid or slushy or frozen solid? Ever since the Voyager spacecraft missions flew through the Jupiter system in 1979, planetary scientists have wondered about the layer of ice surrounding the planet. Europa's blindingly bright ice surface makes it one of the brightest objects in our solar system. Recent Galileo spacecraft images have provided evidence that Europa had a liquid ocean underneath the frozen crust sometime in its history, but it is not clear if this ocean still exists. Of the various explanations proposed by scientists, most scenarios of Europa's evolution have the water layer freezing solid earlier in its history. The moon's surface is -260° F, which could freeze an ocean over several million years. But some scientists are beginning to think that the warming caused by a tidal tug of war with Jupiter and neighboring moons could be keeping large parts of the ocean liquid.

Key images

New stereo and very high resolution images of Europa just transmitted to Earth from the Galileo Europa Mission fly-by in December 1997 may help support the theory that water or slush may slosh beneath Europa's frozen crust. Detailed enough to see a truck-sized object on the surface, the new images are hundreds of times higher resolution than the best Voyager images and three to 20 times higher than earlier Galileo pictures. The Brown and NASA scientists point to three key pieces of evidence from the detailed images:

Oceans and life

"Together, the craters, chaos and wedges support the hypothesis that in Europa's most recent history, liquid or at least partially liquid water existed at shallow depths below the surface of Europa in several different places," says James Head, Brown University professor of geological sciences. "These and other data lend support to the hypothesis that Europa is warm and active today and potentially characterized by a global subsurface water layer or ocean. Europa, like Mars and the Saturn moon Titan, is a laboratory for the study of conditions that might have led to the formation and evolution of life. The combination of interior heat, liquid water, and infall of organic material from comets and meteorites means that Europa has the key ingredients for life, and it represents an exciting environment that is worthy of further detailed exploration."

Crater evidence

Rays and debris from the impact that formed Pwyll Crater radiate over a large part of the moon's surface. Galileo took pictures of the impact crater from two perspectives to determine the three-dimensional shape of the crater. Colleagues at the DLR (German Aerospace Research Establishment) converted these images into a colored map showing the depth of the crater and the height of its peaks. Unlike most young, deep impact craters, the floor of Pwyll is at the same level as the exterior, says Brown graduate student Geoffrey Collins. The central peaks of the crater are more than 2,000 feet high - four times higher than the Washington Monument - and higher than the crater rim. This means that this young crater was warm and weak and collapsed during or very shortly after the meteorite impact, in contrast to craters formed in cold, stiff material. Debris that flowed from the violent impact is dark, suggesting excavation of different material from below the surface. All this suggests that water just beneath the surface was warm enough to be slushy in the moon's recent history.

Chaos evidence

The new images from Galileo help answer some questions about other areas of Europa that are littered with fractured and rotated blocks of crust the size of several city blocks (dubbed chaos terrain). These fractured ice chunks appeared to be either sliding on soft glacier-like ice below the surface or floating like icebergs in a more fluid material. The new images show that the material between the cracked and separated plates of crust is rough and swirly, says Robert Pappalardo, a postdoctoral research scientist at Brown. The pieces are immersed in what appears to be a slush that is now frozen solid. The very low temperatures at the surface of Europa (-260° F) mean that any water exposed at the surface would freeze immediately and might create this kind of texture. The rough chaos terrain, as well as the movement and rotation of the blocks, suggest that the crust was at least partially liquid at shallow depths.

Wedges Evidence

Other images are helping unravel more mysteries. Pieces of the moon's glaringly white crust are separated by wedged-shaped pieces of darker, newer crust, welling up from below, freezing and cracking. The separated pieces of white crust would fit back together like a jig-saw puzzle, suggesting that plate tectonic-like activity might be occurring on Europa to form the wedges. Composed of a set of narrow linear ridges and parallel grooves, the dark wedge has many similarities to new crust formed at mid-ocean ridges on the Earth's sea floor, says Brown graduate student Louise Prockter, who has studied high-resolution sonar images of the Mid-Atlantic Ridge and has visited the Pacific Ocean floor in the research submersible vehicle Alvin. Like Earth, new crust seems to be welling up, separating, and replacing older crust. On Europa, the molten material solidifying on the surface was likely slushy ice or liquid water.

Next Step

To confirm the existence of such a layer, determine its depth and investigate its nature and global extent, further observations are planned for the Galileo Europa Mission, and other experiments are planned for a Europa Orbiter Mission to be launched in 2003, says Michael J. S. Belton of the National Optical Astronomy Observatory in Tucson, Ariz., and team leader for the solid state imaging system.

JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

February 27, 1998

NASA'S CLOSEST-EVER PICTURES OF EUROPA TO BE SHOWN

New images taken by NASA's Galileo's spacecraft during its closest-ever flyby of Jupiter's moon Europa will be unveiled on Mon., March 2, at a briefing to be held at Brown University, Providence, RI. The new pictures, taken during the spacecraft's Dec. 16, 1997 flyby will be available, along with new Galileo animation, on NASA TV and on the Internet. The briefing itself will not be televised.

Europa holds great fascination for scientists because of the prospects that a liquid ocean might lie underneath its icy crust. The presence of water would increase the odds that life may have existed at some point in Europa's history.

Briefing participants describing the new Europa closeups will include Galileo imaging team leader Dr. Mike Belton of the National Optical Astronomical Observatories, Tuscon, AZ, and four Galileo team members from Brown University: Dr. James Head, Dr. Robert Pappalardo, Geoff Collins and Louise Prockter.

The new pictures include high-resolution views of rough, broadly scalloped icy cliffs on Europa as high as Mt. Rushmore. Other images show an impact crater named Pwyll and the so-called Conamara Chaos region, where icy plates on the surface have broken apart and moved around. One large, icy fracture is big enough to be spanned by the Brooklyn Bridge.

New Galileo animation presents a high-resolution look at "wedged terrain" on Europa where new material has risen from below the surface, causing crustal plates to spread and be replaced by newer material. This plate tectonic activity resembles crusts formed in some areas of Earth's sea floor.

The Galileo mission, which continues through December 1999, includes eight Europa flybys, four of the moon Callisto and one or two of the moon Io, depending on the spacecraft's health. The current mission focusing on Europa is a follow-up to Galileo's two-year primary mission through the Jovian system. JPL manages the mission for NASA's Office of Space Science, Washington, DC. JPL is a division of California Institute of Technology.

Images and animation will be transmitted on NASA Television on Mon., March 2 at 9 a.m. and at 12, 3, 6 p.m. (all times Pacific). NASA Television is available through GE-2, transponder 9C at 85 degrees west longitude, vertical polarization, with a frequency of 3880 Mhz, and audio at 6.8 MHz. The new images will be released on the Internet at the following URLs:

http://www.jpl.nasa.gov/galileo/
http://galileo.ivv.nasa.gov/
http://photojournal.jpl.nasa.gov

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