Onde os Ciêntistas procuram vida extra-terrestre no nosso Sistema Solar?

A 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.

Mars invites a deeper look
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.

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.

Europa's ocean: fact or fiction?
A more challenging target for astrobiologists sits farther out in the solar system, where the icy moon Europa beckons with hints of a salty ocean beneath its crusty exterior.

Some studies have suggested that Europa holds an ocean up to three times deeper than Earth's oceans. But other models have suggested that no such ocean exists, and that perhaps the moon only harbors pockets of ice-brine slush. The debate largely depends on how much heat Europa can generate from tidal flexing, when Jupiter squeezes the moon with its gravitational pull.

A recent study suggested that Europa may hold hundreds of times more oxygen than scientists had previously imagined. That has lent to the sense of optimism about prospects for life on the slush ball.