We have long known that water ice, large amounts of it, exists on Mars. We have also long known that billions of years ago, the red planet was much more blue with flowing rivers, large lakes, maybe even oceans.
On Monday, though, NASA announced it has striking evidence of liquid water on the surface of Mars today. In 2011, scientists noticed dark streaks descending along slopes of craters, canyons and mountains in photographs from NASA’s Mars Reconnaissance Orbiter (RSO). The streaks lengthened in the summer, disappeared in the winter and returned the next summer, hence they were dubbed recurrent slope linae (RSL).
Although the best hypothesis was that liquid water was at play in the phenomena, it wasn’t until Lujendra Ojha—a grad student at the Georgia Institute of Technology and lead author on a paper recently published in Nature Geoscience—started analyzing spectrometer data from the RSO that the definitive evidence took shape.
A spectrometer can identify types of molecules by the wavelengths of light they absorb. Unfortunately, the RSL are too narrow for the resolution of the spectrometer to get a direct reading on H2O molecules. The researchers were able to identify hydrated salt molecules near the linae that also disappeared in the winter.
This is all well and good, and exciting on its own account, but the scientific holy grail is not water per se, but the possibility of life that accompanies it.
Everywhere, just about, where water exists on Earth there is life, even in the most hostile environments. A lot of it is microbial, of course, but life nonetheless.
Before we had the technology to study environments such as the deep ocean trenches, we assumed nothing could live there. We are now aware of organisms that defy logic.
Before we started exploring our solar system in earnest, we assumed Earth was the only place liquid water existed. It is now very likely more common than we thought with several moons of the large planets exhibiting signs of subsurface oceans.
Before we had telescopes that could reach out beyond the stars, we speculated that planetary systems such as we have around our star, were probably exceptionally rare.
Even after we started counting the thousands of planets just in our own neighbourhood of the universe, we assumed that if life does exist beyond Earth, only a tiny fraction of the planets in those exceptionally rare solar systems were likely to have given rise to it.
I am committed to the scientific method, so I remain necessarily agnostic on the question of extraterrestrial life since it has not been definitely proven. My very very strong suspicion, however, is that none of these things, solar systems, planets, liquid water and life are the exception, but rather the rule.
In other words, where the conditions for these phenomena exist, they almost certainly exist and the conditions exist pretty much everywhere. While the universe is infinite and, to paraphrase J.B.S. Haldane, stranger than we can even imagine, there is a great deal of order to it as well.
We need to put people on Mars. I would be willing to bet they would find not only water and possibly life, but an extensive and rich fossil record.
