The Red Planet of War has just gotten a little friendlier this week. Detailed observations from the
European Space Agency’s
Mars Express orbiter have revealed the presence of a large lake of water sitting under the planet’s south polar ice cap.
This is exciting news for future exploration of our neighboring planet where the first manned mission of sending astronauts to Mars and returning them safely to Earth is scheduled for the mid 2030s, perhaps 17 years from now.
Liquid water on a long journey is always a good thing to find. You may recall previous research several years ago by NASA found possible signs of intermittent liquid water flowing just under the Martian surface where it may be a little warmer and not subject to evaporation.
Lake beds such as those explored by the Curiosity rover and millions of satellite photographs revealing dry river beds and erosion gullies have shown that water was once present on the surface of Mars in the past but for some reason has now virtually disappeared. Because the planet’s climate is a chilly one, liquid water would be rare because most of its water is locked up in ice.
When I taught Astronomy 101 at GBC we spent a week covering the fourth planet from the Sun. Students learned that the surface temperature of Mars on its equator does not get much above 80 degrees Fahrenheit, even on the hottest of days. Surface probes sent over the last 30 years show an average temperature hovering at a chilly 67 degrees below zero (Fahrenheit), freezing not only water into ice but carbon dioxide into solid dry ice as well.
Such cold temperatures are the result of two factors working in tandem. One, the planet has an ultra-thin atmosphere. Any radiant energy received from the Sun is not trapped as it is on earth but re-radiated back into space. Secondly, the planet has a poor position in the lineup. Because it is roughly 1.5 times the distance from the Sun as Earth, the energy it receives is only 43 percent of what we get per square meter.
The discovery of the subterranean lake was made using MARSIS, a radar instrument on board the orbiter. By beaming a microwave signal to the planet and examining what is bounced back, the surface and immediate subsurface of the planet may be examined for discontinuities due to changing geology. Because a layer of underground water will send back a vastly different signal than solid bedrock, a map could be made of the outline of the water deposit.
The researchers used 29 sets of radar images that showed a region almost a mile below the surface that stretched about 12.5 miles across and looked very similar to lakes that are found beneath Greenland and Antarctic ice sheets on Earth. Although MARSIS wasn’t able to determine how thick the layer of water might be, the scientists estimated it to be a minimum of one meter.
How much population can this underground lake support? That is easy to calculate. Estimates vary, but each person in an average household uses about 80-100 gallons of water per day, most of it used to flush the toilet and take showers and baths. A lake 12 miles in diameter and three feet deep holds 76 billion gallons of water. This could last a colony of a thousand space explorers two thousand years without recycling!
But, in order to remain liquid in such cold conditions, perhaps as low as -20 Fahrenheit, it is conjectured that the water likely has a great deal of salt dissolved in it and this would have to be filtered out, perhaps by a reverse osmosis mechanism. On Earth subsurface lakes are known to exist below the Antarctic ice sheet even though the mean annual surface temperature is 76 degrees below zero Fahrenheit. Perhaps a pipeline to this reservoir will be built someday to tap this resource.
Could there be life in this lake?
“It’s plausible that the water may be an extremely cold and concentrated brine, which would be pretty challenging for life,” explained Dr. Claire Cousins, an astrobiologist from the University of St Andrews, UK. In other words, without the benefit of sunlight to spur organic reactions on, the prospect for any biological activity as we know it is rather dim. Still, the presence of blind cavefish here on Earth, such as the Mexican tetra, living comfortably for millions of years, never feeling the warmth of a summer day, makes this water lake finding very intriguing.
Because Mars is in opposition on July 27, when the Earth moves between Mars and the Sun the planet will appear as a very bright and reddish star-like object shining over the southeastern horizon. This will be its brightest for the next 17 years.