On Monday, September 28, NASA announced the discovery of flowing liquid water on Mars.

The search for extraterrestrial life is limited by what is currently known about life. And life “as we know it” requires water, nutrients, and an energy source. With the present understanding of life, astrobiologists generally believe that, where there is water, there is life.

The incredible data gathered by various missions provides strong evidence that ancient Mars was habitable, and that present Mars could be habitable as well.

The recent announcement about flowing water on Mars is exciting, and it increases the likelihood that Mars is home to extraterrestrial life. Scientists say that dark streaks running down Martian slopes are formed by salty liquid water. These streaks, known as recurring slope lineae (RSL), appear seasonally and have been detected at different locations across the planet.

RSL on Mars. (Credit: NASA/JPL-Caltech/Univ. of Arizona)

RSL on Mars. (Credit: NASA/JPL-Caltech/Univ. of Arizona)

As Space.com explains, “RSL appear during warm weather but fade away when temperatures drop, leading many researchers to speculate that liquid water is involved in their formation.”

But NASA and various scientific research teams have been talking about RSLs and flowing water on Mars for years.

In 2011, NASA announced that data collected by the Mars Reconnaissance Orbiter (MRO) suggests flowing water on Mars during the planet’s warmest months. NASA’s press release discussed RSLs in MRO images that show “dark, finger-like features” that “appear and extend down some Martian slopes during late spring through summer, fade in winter, and return during the next spring.” At that time, Alfred McEwen of the University of Arizona and principal investigator for the HiRise camera aboard NASA’s MRO commented, “The best explanation for these observations so far is the flow of briny water.”

In 2013, soil samples analyzed by NASA’s Curiosity rover suggested “abundant, easily accessible water” widespread across Mars. Also in 2013, researchers announced that data from Curiosity supported the notion that perchlorate, a chlorine-containing chemical detected on Mars by NASA’s Phoenix lander in 2008, is widespread across the planet. Doug Archer, a scientist with the Astromaterials Research and Exploration Science Directorate of NASA’s Johnson Space Center, commented that “the implications of globally distributed perchlorates are very important for climate, habitability and present-day aqueous processes.”

The NASA Astrobiology institute and the UK Centre for Astrobiology co-hosted a conference in 2013 titled “The Present-Day Habitability of Mars.” At the conference, McEwen discussed HiRise’s RSL observations, and there too he suggested that briny water may flow down steep slopes on Mars during the planet’s spring and summer. He also commented, “We certainly can’t rule out the possibility that [Mars is] habitable today.”

RSL on Mars. (Credit: NASA/JPL/University of Arizona)

RSL on Mars. (Credit: NASA/JPL/University of Arizona)

In 2014, a study conducted by the University of Michigan concluded that “water, near and on the surface of Mars, melts rapidly enough when combined with salt to allow bacterial life to flourish, despite the freezing temperatures on the planet.”

Needless to say, researchers have published several studies about RSLs and flowing water on Mars. So why is NASA making a big deal about something already known?

Data collected by an instrument aboard the MRO, called the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), allowed the research team to analyze the mineralogical makeup of the planet’s surface. “What we found was that at times and places when we see biggest RSL on the surface of Mars, we also found spectral evidence for hydrated salts on the slopes where RSL form,” details study lead author Lujendra Ojha. Space.com explains, “Hydrated salts precipitate from liquid water, so detecting them is a big deal — especially since circumstances make it unlikely that CRISM could spot RSL water directly.”

These salts were also determined to be perchlorates, which lower the freezing point of water from 32 degrees Fahrenheit to negative 94 degrees Fahrenheit.

Although previous studies suggest the strong likelihood of flowing water on Mars, this latest research, published in the journal Nature Geoscience, provides even more evidence to support that notion, as well as the claim that perchlorates are widespread across the planet.

The habitability of Mars seems to improve with each new study. The countdown for the discovery of extraterrestrial life is on.