A robot on Mars has just turned up the best evidence yet that liquid water once flowed on the Red Planet. Because water is thought to be necessary for life, the discovery should help researchers pinpoint places where living things might have once survived.
The search for water and life on Mars has picked up in the last few weeks, ever since two rovers landed safely on opposite sides of the planet in January. The rovers, called Spirit and Opportunity, are exploring their rocky neighborhoods, taking pictures, making observations, and sending back information to scientists on Earth.
This close-up of a rock shows rounded grains that indicate a wet history for Mars.
NASA/Jet Propulsion Lab/U.S. Geological Survey
The new signs of water came from Opportunity, which has been creeping across a huge plain called Meridiani Planum. Images of the view through Opportunity's magnifier showed tiny round grains embedded within layers of rock. Other images unveiled weird holes poking through the stone. Such holes form in rocks on Earth when minerals crystallize out of water, then get washed out or eroded away.
A piece of equipment called a spectrometer revealed pockets of sulfur compounds, which could form only if a salty liquid once soaked through the dirt, then evaporated. Another type of spectrometer turned up an iron-rich mineral called jarosite, which occurs on Earth in hot springs or acidic lakes.
Taken together, the new evidence has inspired scientists to develop ways to bring Mars rocks and dirt back to Earth for further study. Because all the liquid water seems to be gone from the planet's surface, however, few researchers expect to find even microbes lurking there now, let alone human-sized aliens.
For more dramatic alien encounters, you still have to count on TV, books, or your own imagination.E. Sohn