Going with the flow on Mars

This undated photo provided by NASA shows dark, narrow, 100 meter-long streaks on the surface of Mars that scientists believe were caused by flowing streams of salty water. (NASA/JPL/University of Arizona via AP)

Nobody knows for sure if life exists on Mars. But if it does, it could probably only thrive somewhere below the dusty, frigid surface. And new evidence suggests that possibility may not be so far-fetched.

On Monday, NASA scientists announced the discovery of what they believe is flowing water on Mars’ surface. Seasonal rivulets form in warmer months and dry up by the Martian winter, leaving behind darks streaks in the dust.

It’s only enough water to dampen the dust ­— not exactly a babbling brook — but it is an exciting discovery nonetheless.

Indeed, it’s only the latest intriguing find in a dramatic season for space exploration. This summer brought the first close-up photos of Pluto, revealing a far more varied and interesting surface geography than scientists had expected. A visit to the dwarf planet Ceres revealed mysterious glowing patches, which scientists are still unable to conclusively explain.

Of course, evidence of water on Mars is hardly new. The planet has a vast polar ice cap, and water vapor makes up a small part of its thin atmosphere.

But this is the first time flowing water has been observed. Now scientists are wondering about its source.

It could be that the water bubbles up from underground aquifers where it sits frozen during cold months and melts when the surface warms. Or it could be that certain salts on the surface draw water vapor out of the atmosphere until enough condenses to form a small stream.

Either way, the water would have to be extremely salty to remain liquid at temperatures far below freezing.

If, however, there is a store of liquid, salty water somewhere underneath the surface of Mars, it could be an ideal place for life to take hold.

On Earth, microbes have adapted to live in the harshest environments — beneath hundreds of feet of ice in Antarctica, in thermal vents on the ocean floor and in the world’s driest deserts.

That incredible tenacity and adaptability raises hopes that life may be common throughout the universe. Mars probably isn’t even the best candidate in our own solar system.

Icy moons like Titan, Enceladus and Europa ­— the first two orbit Saturn and Europa orbits Jupiter ­— are thought to contain subsurface oceans full of life-giving organic compounds. The gravitational pull exerted by Saturn and Jupiter may be strong enough to create a tidal force to heat the water and keep it in a liquid state.

NASA plans to send a probe to Europa within the next few years, which should give scientists a better idea of whether or not that moon might be able to support life.

In the meantime, Mars will continue to be a focus for NASA as the agency looks toward a manned mission sometime in the next two decades.

Private enterprises like Mars One aim to set up a permanent colony on the Red Planet, populated with volunteer explorers.

Moving next door in our planetary neighborhood sounds a little extreme.

But the rest of us can enjoy the thrill of discovery that comes with understanding the universe just a little bit better.