For those of us who wonder whether life once existed on Mars either in the ancient past or present day, there is a particular feature that piques our interest. <\/p>\n
It is a massive feature Valles Marineris, the Grand Canyon of Grand Canyons. <\/p>\n
The Red Planet may be decidedly smaller than our homeworld, but it is home to some truly gargantuan features, including Valles Marineris and Olympus Mons, an enormous volcano. <\/p>\n
The former stretches the length of Los Angeles to New York, if we could somehow transport the United States to Mars. Arizonas Grand Canyon is, well ... its a bit smaller than that. <\/p>\n
Here are some hard numbers. Valles Marineris is 4 miles deep, up to 370 miles across and 2,500 miles long. <\/p>\n
The Grand Canyon, in comparison, is 1 mile deep, 18 miles wide and 280 miles long. <\/p>\n
I dont need to tell you that this is an enormous feature. <\/p>\n
So you think of something four time as deep as the Grand Canyon. About 20 times wider. And much, much longer. <\/p>\n
Valles Marineris is a crack in Mars surface forged as the planet cooled that covers 1\/5th of the planets circumference, said Rick Davis, assistant director for science and exploration in NASAs Planetary Science Division. Subsequently, it offers unprecedented insight into the geological history of the Red Planet. <\/p>\n
The valley offers a mural of Martian history that would captivate geologists and astrobiologists alike with rock strata that stretch back to the days when Mars was still wet. <\/p>\n
Imagine being at the bottom of that forever-deep canyon and being able to peer into Mars ancient past. What might be found down there? First and foremost, though, what are the possibilities of sending scientific instruments down to study Mars past life? <\/p>\n
While the opportunities for science are tantalizing, the challenges of landing in such a deep canyon with imprecise guidance, navigation and control (GNC) systems are signficiant, Davis said. <\/p>\n
For any landing site, we have a desired landing spot, but due to limitations in our GNC systems and our understanding of Martian winds and atmospheric density, the actual landing can occur anywhere within an ellipse which we refer to as a landing error ellipse. <\/p>\n
Initial landing error ellipses at Mars were very large. For Viking, the first successful lander at Mars, the error ellipse was 174 x 62 miles. But, the precision of our landing systems has improved over time. Curiositys error ellipse was just 15 x 12 miles. <\/p>\n
There is another upcoming rover mission to Mars, called Mars 2020, that will conduct geological surveys, determine environmental habitability, search for signs of ancient Martian life and assess the risk and reward humans face in colonization. <\/p>\n
Davis said the Mars 2020 team is trying to reduce the error ellipse to an even smaller 11 x 8 miles. There was a site at Valles Marineris considered as a possible landing site, but it was judged to be too small (6 miles across at its narrowest). <\/p>\n
In the meantime, scientists have come up with a short list of three potential landing sites: Northeast Syrtis (a very old part of the planet), Jezero Crater (once home to an ancient lake) and Columbia Hills, which possibly once held a hot spring long, long ago. <\/p>\n
In other words, Valles Mariners is pretty much out. For now, anyway. <\/p>\n
But not all hope is lost. Davis said that human landings will demand pinpoint accuracy; accuracy, in other words, that would be conducive to landing inside the giant canyon. <\/p>\n
Of course, we dont know exactly when we will be able to send humans to Mars, but, as far as decades go, it will probably happen quite soon. <\/p>\n
For now, we can only imagine what well find in the most ancient strata of Valles Marineris. <\/p>\n
Perhaps there is a discovery waiting that will change the course of history; one that will alter our view of our place in the solar system and its past. <\/p>\n
<\/p>\n
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