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Beyond Our Planet

Since NASA studies both Earth and other planets, what we learn from Earth's oceans can help us make sense of clues to the watery pasts of other planets. Water is essential at the molecular level to moving life beyond its basic building blocks; thus, searches for extraterrestrial life usually involve a search for liquid water.

H2O content of Mars' north pole
This map centered on the north pole of Mars is based on gamma rays from the element hydrogen - mainly in the form of water ice. Regions of high ice content are shown in violet and blue and those low in ice content are shown in red. The very ice-rich region at the north pole is due to a permanent polar cap of water ice on the surface. Credit: University of Arizona.

Mars is a cold desert planet that currently has no liquid water on its surface. Yet the terrain of Mars suggests that the red planet once had much more water on its surface than it does today. Some scientists wonder whether Mars may have had an ocean in its northern hemisphere long ago. While the word is still out on that, recent spacecraft findings have shown rocks that only could have formed in the presence of water, as well as evidence of lakebeds and other interesting features associated with water.

Discoveries made by the Mars Odyssey orbiter in 2002 show large amounts of subsurface water ice in the northern arctic plain. In 2008, the Phoenix Mars Lander will investigate this circumpolar region using a robotic arm to dig through the protective top soil layer to the water ice below and ultimately, to bring both soil and water ice to the lander platform for sophisticated scientific analysis.

During the Galileo mission to Jupiter, its magnetometer observed the moon Europa. Strangely, it got a magnetic signal. Planetary scientists have deduced that Europa does not have enough mass to contain a metallic core, which would ordinarily be necessary for a body to produce its own magnetic field. So how could Europa have a magnetic field? The relatively weak field Galileo observed is consistent with what could be conducted by liquid salty water. Like an ocean.

Europa
False-color composite of Europa. Bright plains in the polar areas (top and bottom) are shown in tones of blue. Long, dark lines are fractures in the crust, some of which are more than 3,000 kilometers (1,850 miles) long. The bright feature containing a central dark spot in the lower third of the image is a young impact crater some 50 kilometers (31 miles) in diameter. Credit: NASA/JPL

But the surface of Europa is far too cold for liquid water to exist. Water may reside under the crust - the constant heaving of the moon as it's subjected to Jupiter's brutal gravity may produce enough heat to keep salt water in liquid state.

Europa is thought to be one of the most promising places to search for microscopic life in our solar system. The ice-covered world may have liquid water, energy, and organic compounds - all three of the ingredients necessary for life to survive.

Sometimes the search for extraterrestrial life takes place right here on Earth. Parts of the ocean are nearly as extreme as the environments we could find elsewhere in the solar system - and they contain life! Not puppies or kittens or even goldfish of course - they contain creatures called "extremophiles". These creatures live in harsh environmental conditions: hot, with a lot of extremely active volcanoes, and with little to no oxygen in the atmosphere. Today varieties of extremophiles are found thriving in circumstances once thought inhospitable to life, such as hot springs and deep ocean thermal vents. Studying extremophiles on Earth helps scientists design experiments to search for life on other planets.