Is There Water (or Life) on Mars?
Does new evidence show that liquid water could be present on Mars now? Does this mean humans might one day call the planet home?
Sabrina Stierwalt, PhD
Listen
Is There Water (or Life) on Mars?
NASA recently made an announcement that a major mystery from Mars had been solved and that an official announcement with more details would be made in a few days. Despite an accidental early leak of the press release, the big news was announced yesterday and set the astronomy community abuzz: planetary scientists have found evidence of liquid water on the surface of our neighbor, the Red Planet. What does this mean for the potential for life on Mars?
Why the Focus on Liquid Water?
Having not uncovered any evidence for its existence so far, we can be sure there is no other intelligent life in our solar system. Earthlings are hard to miss. We have been sending radio emissions out into space in the form of television broadcasts, satellite communications, and even radar to study other planetary surfaces for decades now. We would expect any other similarly intelligent civilizations to do the same. In fact, searches for intelligent life outside of our solar system have been largely focused on searches for radio emission.
Thus, the search for life in our own solar system is really the search for the potential for life. This potential could come in the form of more simplistic organisms like microbes, but it usually means looking for the conditions necessary to sustain life.
Liquid water is required for the most basic processes that create and sustain life. The presence of liquid water thus directly assesses the chances that we could call a planet or other astronomical body “home.”
Water is surprisingly abundant in our solar system but usually in the form of water vapor on Venus or in the form of ice—for example in comets or distant Kuiper Belt objects far from the Sun’s heat. Even Mercury, the closest planet to the Sun, is able to sustain polar ice caps because they escape direct exposure to our star’s heat.
Until yesterday, the most promising hosts to liquid water in our solar system were Europa, one of Jupiter’s large moons, and Enceladus, a dynamic moon in the Saturnian system. Both moons show signs of having water below their icy crusts that is kept in liquid state thanks to hydrothermal activity caused by the tides due to their gas giant planetary hosts. Both also show evidence of erupting geysers, spewing that liquid water from below up and out over the surface.
But what about places a bit closer to home? So far, space travel has only taken humans as far as the Moon, much closer than the distances required to reach the outer solar system.
Was There Liquid Water on Mars in the Past?
The Mars Exploration Rovers, Spirit and Opportunity, landed on Mars in 2004 on a mission to find evidence that water once existed on the planet. NASA scientists and engineers hoped the mission would last 90 Martian days (about 92.5 Earth days or 3 Earth months). More than ten years later, the Opportunity Rover has traveled farther than a full marathon distance of 26.2 miles and continues to send us new information about the planet. Spirit’s mission also surpassed expectations by more than 20 times and continued to roam Mars while collecting data until 2009 when it became stuck in soft soil. Its last communication was in 2010.
A third rover, Curiosity, landed on the planet in 2012 as part of NASA’s Mars Science Laboratory mission. Curiosity is continuing the MER efforts to determine the role water plays in the geology and history of Mars and acts as a prototype for the upcoming Mars 2020 mission which will look for liquid water beneath the surface. Curiosity’s findings will also aid the preparation of future human exploration of the planet.
In their explorations of Mars, Spirit and Opportunity found various geological features that strongly suggest liquid water once flowed on the surface in the history of the planet. The soil shows evidence of having been carved into patterns that mimicked those seen where water flows on Earth. That soil also appears to be hydrated: it contains compounds that are consistent with being left behind after the evaporation of ancient surface oceans.
Is There Liquid Water on Mars Now?
Most of this evidence was either circumstantial or could only suggest that liquid water once existed on Mars in the past. That began to change around 2011, when the Mars Reconnaissance Orbiter (MRO), an observatory orbiting the Red Planet, returned images showing dynamic features on the surface: dark streaks that grew in the summer and disappeared by fall. Planetary scientists observed these features over several years, and their changing nature, as well as the shape and positioning of the streaks, suggested they could be associated with the flow of liquid water.
However, water was only a best, and perhaps hopeful, guess. Nothing was known about the chemical makeup of these dark streaks, officially termed recurring slope linae (or RSLs for short) until the findings released yesterday. An instrument aboard MRO known as a spectrograph observed how these features interact with light. Spectrographs reveal how much light is emitted or absorbed at different wavelengths, and each molecule produces specific and distinct features in its spectrum.
The MRO spectroscopic observations showed dips or absorption features in the spectra for the RSLs consistent with having been produced by hydrated salts – salt crystals with liquid water trapped inside. This salty water signature was also found to be strongest when the streaks were largest, solid evidence that the two are linked and that the salt water is part of a current, dynamic process.
Even more intriguing is the fact that this briny water has a larger range of temperatures at which it can remain a liquid (i.e. without boiling off into vapor or freezing into ice). This larger temperature range thus increases the possibility of stability of liquid water on Mars.
Want More Mars?
This Friday marks the release of The Martian in theaters. Matt Damon stars as an astronaut left behind on the Red Planet during a mission who is then forced to survive there on his own. NASA will host multiple press conferences associated with the event, called So You Want to be a Martian and Surviving on Mars. You can find more Mars news at NASA Mars and follow the conversation on Twitter at the #JourneytoMars and #AskNASA hashtags.
Until next time, this is Sabrina Stierwalt with Ask Science’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Ask Science on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.comcreate new email.
Images courtesy of nasa.gov
