Water Still Flows on Mars
Tuesday, September 29th, 2015September 29, 2015

Mars. (NASA/JPL/Malin Space Science Systems)
The solar system just got a little bit wetter. Yesterday, scientists from the National Aeronautics and Space Administration (NASA) reported that water flows on Mars during warm seasons. They made the finding using a probe called the Mars Reconnaissance Orbiter (MRO).
Mars is the fourth planet from the sun. The planet is one of Earth’s “next-door neighbors” in space. Scientists have long suspected that water flowed on Mars in the distant past. Probes and rovers had found minerals on its surface that only form in the presence of water. Ice had also been discovered on Mars, both at the poles and other places on the planet.

In this illustration of our solar system, Mars is the fourth closest planet to the sun. Scientists have known for a while that Mars had liquid water on its surface at one time, but that Mars still has water at its surface today is an exciting discovery. (World Book illustration by Precision Graphics)
In August 2005, NASA launched the MRO, which arrived in orbit around Mars in March 2006. The craft was designed to study the planet’s structure and atmosphere and to identify potential landing sites for lander and rover missions. Scientists used the MRO’s instruments to observe mysterious dark streaks on Martian hillsides which appear to ebb and flow over time. The streaks darken in the warm season, when temperatures can exceed -10 °F (-23 °C).
The MRO revealed that these dark streaks were caused by liquid water saturated with salts. Salts lower the freezing point of water. This is why people in colder climates salt sidewalks in winter, and why oceans can stay liquid below the freezing point of pure water. In the warmer periods on Mars, the salts allow frozen water to melt and flow just under the surface of the hills. Some of the water wicks to the surface, forming dark spots.
The detection of liquid water on Mars will revitalize the search for current, as well as past, life on the planet. All known life needs liquid water to survive, so its presence on the Red Planet hints that life could possibly exist there today. Scientists are eager to continue the search for life, but also wary: liquid water on Mars will make it easier for organisms from Earth to colonize the planet. If probes land in these areas, bacteria could hitch a ride along with them and spread to the Martian surface, potentially changing or wiping out any native life that might exist there. Thus, space agencies may have to study such areas from a distance.
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