Europa's Mysterious Ice Domes May Provide Clue to Signs of Life 

A research team from the University of Colorado at Boulder has identified giant ice domes scattered on the surface of Jupiter's moon Europa, which according to the team could be the places to search for signs of life. The domes are huge - some more than four miles in diameter and 300 feet high - and are found in clusters on Europa's surface, said Amy Barr, a doctoral student at Colorado and a member of the research team. It is thought that Europa harbours an ocean beneath its icy surface. 

"It is possible that any present or past life or even just the chemistry of the ocean may be lifted to the surface during the formation of ice domes," said Barr. "It could be an elevator ride for microbes that might inhabit the ocean." "Till date, we believed that the ice domes might have been solely carved by a geological process called thermal upwelling," said Robert Pappalardo, an assistant professor of astrophysics and planetary sciences who led the team at Colorado. "This process pushes the warmer ice underneath to the surface." 

But, images taken by Nasa's Galileo spacecraft make Pappalardo and his colleagues to revise their theory. Pappalardo and teammates now believe that small amounts of impurities such as sodium chloride or sulfuric acid may contribute to the thermal upwelling that forms the ice domes. Such handiworks of nature abound on earth. This provided clue to Pappalardo's conjecture. On earth, similar domes form in clumps in arid regions. Here on earth, it is salt that is buoyant enough to move up through cracks and fissures in rock formations to form dome clusters at the surface. 

According to them, equivalent of table salt or battery acid could melt ice at low temperature allowing more pristine ice blobs to crack open the icy surface and create domes. "We have long been puzzled by the ice blobs that push up through the frozen shell of Europa, which is likely about 13 miles thick," said Pappalardo. "Infrared and colour images taken by Galileo spacecraft seem to indicate some of ice on the surface of these Europa's domes is contaminated." According to him, this means that impurities seen at the surface are clues to the internal composition of the Jovian moon, telling a salty ice shell. A paper on the subject co-authored by Pappalardo and Barr was presented at the annual meeting of Division of Planetary Sciences held on September 2 - 6 in Monterey in California. DPS is an arm of the American Astronomical Society. 

As Europa revolves around Jupiter in an elliptical path, it has strong tidal action. This tidal force may have been also playing a role in causing such ice domes. "This force is strong enough to squeeze the moon and heats its interior," said Pappalardo. "As a result, warm ice blobs rise upward through the ice shell toward the colder surface, melting out saltier regions in their path." The less dense blobs, he said, can continue rising all the way to the surface to create the observed domes. 

For lay people, it is difficult to grasp what is happening out there on Europa. For this Barr drew a wonderful analogy. According to her, the upwelling of warmer ice from the inner ice shell to its surface resembles to that of a pot of boiling spaghetti sauce. "The burner under the pan sends the hottest sauce to the top, creating the bubbles at the surface," she said. "The trouble is Europa's icy skin is as cold and as hard as a rock." But the presence of small amounts of salts or sulfuric acid could be a troubleshooter. "In fact, our models now show that the upwelling of warm ice in the frozen shell's interior, combined with small amounts of impurities such as sodium chloride or sulfuric acid, would provide enough of a force to form these domes," said Pappalardo. 

But what is about the conjecture of life? Jupiter constantly emits powerful radiation, which baths the Europa's surface. "This precludes any life on the Europa's surface," said Barr. "But a spacecraft might be able to detect signs of microbes just under the surface." Pappalardo is also collaborating with a Nasa team engaged in developing goals for the Jupiter Icy Moons Orbiter mission. The mission will not only confirm the presence of an ocean at Europa, but also remotely measure the composition of the surface. At the same time, it will search for potential landing site for future lander missions.