Finding Water on Mars

Water on Mars: Important in the Movies and Reality!

Mars slopes linae
Dark narrow streaks, called "recurring slope lineae," emanate from the walls of Garni Crater on Mars, in this view constructed from observations by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. The dark streaks here are up to few hundred yards, or meters, long. They are hypothesized to be formed by flow of briny liquid water on Mars. NASA/JPL-Caltech/Univ. of Arizona

 Ever since we began the exploration of Mars with spacecraft (back in the 1960s), scientists have been on the lookout for evidence of water on the Red Planet. Each mission gathers more evidence for the existence of water in the past and present, and each time definitive proof is found, scientists share that information with the public. Now, with the popularity of Mars missions on the rise and the amazing story of survival that moviegoers have seen in "The Martian", with Matt Damon, the search for water on Mars takes on additional meaning. 

On Earth, definitive proof of water is easy to find — in as rain and snow, in lakes, ponds, rivers, and the oceans. Since we haven't visited Mars in person yet, scientists work with observations made by orbiting spacecraft and lander/rovers on the surface. Future explorers WILL be able to find that water and study it and use it, so it's important to know NOW about how much there is and where it exists on the Red Planet. 

Streaks on Mars

Over the past few years, scientists noticed curious-looking dark streaks that appear on the surface on steep slopes. They seem to come and go with the change of seasons, as temperatures change. They darken and appear to flow down the slopes during periods when the temperatures are warmer, and then fade out as things cool down. These streaks appear in several locations on Mars and have been called "recurring slope linae" (or RSLs for short). Scientists strongly suspect they're related to liquid water that deposits hydrated salts (salts that have been in contact with water) on those slopes. 

Salts Point the Way

Observers took a look at the RSLs using an instrument onboard NASA's Mars Reconnaissance Orbiter called the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). It looked at sunlight after it had been reflected from the surface, and analyzed it to figure out what chemical elements and minerals were there. The observations showed the "chemical signature" of hydrated salts in several locations, but only when the dark features were wider than usual.  A second look at the same places, but when the swaths were not very wide didn't turn up any hydrated salt. What this means is that if there's water there, it's "wetting" the salt and causing it to show up in the observations.
What are these salts? Observers determined that they are hydrated minerals called "perchlorates", which are known to exist on Mars. Both the Mars Phoenix Lander and the Curiosity rover have found them in the soil samples they've studied. The discovery of these perchlorates is the first time these salts have been spotted from orbit over several years. Their existence is a huge clue in the search for water.

Why Worry about Water on Mars? 

If it seems that Mars scientists have announced water discoveries before, remember this: the discovery of water on Mars has not been one single discovery. It is the result of many observations over the past 50 years, each one giving more solid evidence that water exists. More studies will pinpoint more water, and eventually give planetary scientists a much better handle on how much water the Red Planet has and its sources underground. 

Ultimately, people will travel to Mars, perhaps sometime in the next 20 years. When they do, those first Mars explorers will need all the information they can get about conditions on the Red Planet. Water, of course, is important. It's essential to life, and it can be used as a raw ingredient for many things (including fuel). Mars explorers and inhabitants will need to rely on the resources around them, just as explorers on Earth had to do as they explored our planet. 

Just as important, however, is to understand Mars in its own right. It's similar to Earth in many ways, and formed in roughly the same region of the solar system some 4.6 billion years ago. Even if we never send people to the Red Planet, knowing its history and composition help fill in our knowledge of the solar system's many worlds. In particular, knowing its water history helps fill in the gaps of our understanding about what this planet may have been in the past: warm, wet, and much more habitable for life than it is now.