Water Discovered on Mars

A portrait of NASA’s Curiosity rover taken on Sol 2082 (June 15, 2018). A Martian dust storm has reduced sunlight and visibility at the rover’s location in Gale Crater.


Since Christian Huygens first described the Hourglass Sea on Mars in 1659, it has been accepted that Mars has water. In 1858, canals were described as leading from the sea in straight lines, which changed with the seasons. This indicated some form of advanced life present on Mars to create and change these straight canals. It wasn’t until telescopes improved that Mars was seen to be dry and, in 1909, the canals theory was officially debunked. The Hourglass Sea was renamed Syrtis Major – the dark spot on Mars made from basaltic volcanic rocks from a low-relief shield volcano (dark rocks from an old lava flow). With clearer images of Mars coming all the time, the idea of water on Mars – and the life forms expected to accompany it – were put to rest.

But the search for water continued. From the Mariner and Viking missions of the ’60s and ’70s to the landers and rovers of the modern day, there have been tests and photos taken looking for liquid water. And last week, an article was published in the journal Science that finally announced the detection of liquid water on Mars.

“The presence of liquid water at the base of the Martian polar caps has long been suspected but not observed. We surveyed the Planum Australe region using the MARSIS [Mars Advanced Radar for Subsurface and Ionosphere Sounding] instrument, a low-frequency radar on the Mars Express spacecraft,” the paper states. “Radar profiles collected between May 2012 and December 2015 contain evidence of liquid water trapped below the ice of the South Polar Layered Deposits. Anomalously bright subsurface reflections are evident within a well-defined, 20-kilometer-wide zone centered at 193°E, 81°S, which is surrounded by much less reflective areas. Quantitative analysis of the radar signals shows that this bright feature has high relative dielectric permittivity (>15), matching that of water-bearing materials. We interpret this feature as a stable body of liquid water on Mars.”

Roberto Orosei of the Istituto di Radioastronomia, Istituto Nazionale di Astrofisica, in Bologna, Italy, along with 21 of his colleagues, published the article in the July 25 issue of Science and, since then, the news has exploded around the world.

And rightly so. This is a big deal, not just for science, but for a larger understanding by humans of our planetary neighbor.

“It is an exciting interpretation for a variety of reasons. One, obviously, is the implication for the possibility of extant life on Mars,” said Daniel Nunes, research scientist at Jet Propulsion Laboratory and investigation scientist for both the SHARAD and RIMFAX instruments on the Mars Reconnaissance Orbiter and Mars 2020 missions, respectively. “Another is that it offers us a clue on how warm the interior of Mars is currently. Planetary scientists have speculated in the past that if ice is present in the subsurface of Mars, it could be the case that the subsurface is warm enough to melt it. The question is how warm and how deep.”

Geothermal heat is a debate in itself in that it has been speculated in the past that Mars may be entirely dead inside, leading to the drop off of the magnetic field surrounding the planet and leaving the surface exposed to solar winds and harsher energies. If there is subsurface heat, that means that Mars isn’t dead, just lying dormant or with reduced heat levels compared to Earth.

Another aspect of the freezing and melting of liquid water is the salinity of the water. On the surface, it gets cold enough to freeze carbon dioxide – down to -115°F. This thin layer of CO2 ice covers the existing subpolar liquid water. But down below the ice sheets, the water may be more salt-rich, which affects the temperature of freezing.

“Salinity lowers the freezing point of ice to below the usual 32°F or 0°C. The implication is that if you have salt the amount of heat coming from the interior of Mars does not have to be as much in order to melt the ice. In the case of the MARSIS finding, the relatively compact size of the radar-bright feature begs the question of why it is compact and why there. Help from enhanced salinity at that location is definitely a possibility,” Nunes said.

With the discovery of water, the first question many thought was the same that humans thought last time evidence of water was found on Mars: is there life? But with as much time as JPL has explored Mars, the idea of what kind of life might be found has changed. Suffice it to say, it won’t be any time soon that Martians will be seen pontooning on the newly discovered lake.

“Little green men of the ‘We come in peace, we come in peace’ variety (as in ‘Mars Attacks’) is very, very unlikely. Microbial life is a more plausible possibility, but it is too early to attempt to answer this question. But the time is right to ask it and examine it,” Nunes said.