Aryanews- The dusty red planet and an icy moon of Jupiter may hold the best hopes for scientists trying to track down extraterrestrial life, at least in this solar system.
Mars and Europa each hold the promise of liquid water and possibly life. Mars has a history that suggests water once flowed in rivers and lakes, and it may still harbor liquid water deep underground. The more distant Europa could hide a churning ocean filled with life forms beneath its icy surface, as the moon gets gravitationally squeezed by Jupiter.
Future space missions have targeted both destinations to send new robotic explorers. But the red planet represents a much closer and better known target for space explorers.
"We're much farther down the road with Mars than Europa," said Jack Farmer, an astrobiologist at the University of Arizona.
Liquid water probably once filled the valleys and basins on Mars, but now the planet's surface resembles a barren, dusty badland. Any living organisms that may have existed must have gone extinct or underground.
"My view is that habitable environments on Mars are likely to only be found in the deeper subsurface where we might have a hydrosphere," Farmer told SPACE.com. "Liquid water is unstable at the surface of Mars today."
Some ice water or snowfall could temporarily become liquid at the surface, such as when NASA's Phoenix Mars Lander possibly found some liquefied globules clinging to its struts. Still, that would hardly last long enough under freezing or vaporizing conditions to sustain life.
Microbial life that could eke out an existence also seems unlikely to survive the cosmic radiation that scours the surface of Mars. But astrobiologists remain excited about possibly finding signs of past life on the surface, where minerals that only form in water may have preserved certain remains.
"A lot of these kinds of mineralogical targets are water indicators, and we know where a lot of these deposits are now," Farmer said. He noted that sulfate minerals do a decent job of preserving organic compounds produced by organisms on Earth, and sometimes even microfossils. Silica and other clay minerals have also turned up during searches by the Mars rovers and orbiters.
Upcoming missions to Mars could perhaps even tap into any liquid reservoirs hidden deeper below and search for existing life, if they have the right equipment.
