Right now, 140 million miles away, somewhere on the frigid surface of Mars, there is water forming. Scientists announced they have strong evidence that briny water flows on the planet, a critical step toward identifying possible life on Mars.
“Water is essential to life as we know it,” wrote Lujendra Ojha, Mary Beth Wilhelm, and their co-authors in a paper published Monday in Nature Geoscience. “The presence of liquid water on Mars today has astrobiological, geologic, and hydrologic implications and may affect future human exploration.”
If this announcement, which NASA billed as “major” in the days leading up to it, sounds not altogether new, it’s because scientists have been obsessing over the water on Mars for decades. (The sight of ice volcanoes on Pluto this summer had scientists similarly elated.) Astrobiologists have long suspected that Mars was at least partially covered in water at one time—markings on the planet indicate the presence of ancient streambeds. A billion years ago, scientists believe the planet had a roiling, primitive ocean. Meandering formations on the surface of Mars suggested water flowed on the planet for a geologically significant period of time. Long enough, perhaps, to have sustained bacteria or other simple life forms.
In recent years, it became increasingly clear that water in some form was still present on Mars—in vast near-surface deposits of ice, in massive glaciers near the poles, and in large sheets in crater and gullies. The knowledge that water existed at all on Mars “completely shifted the paradigm of Mars today from a static, arid world to a planet still being shaped by water. If life evolved there, conceivably it may still survive,” as the Mars Exploration Program Analysis Group put it.