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Mars: once upon a green planet
IT is no longer wishful thinking or science fiction to imagine the Red Planet as once being a world containing water. Though scientists did have clues to Mars once having liquid water billions of years ago after the many tell tale images but the fact has only being established recently.
Nasa’s rover Opportunity has discovered water in the Martian rocks. Was the area named Merdiani Planum by the science team, once a giant sea or did the water seep into the rocks from underneath? It is a question that the scientists are trying to answer. So far, Opportunity has been inside a shallow crater-like depression in the ground and has been studying an outcrop. An outcrop that once contained water in some form.
The rover is supposed to head for another site called the “Endurance” crater, which has the same width as the length of a football field. It is possible that the bedrock is older and thicker than opportunity’s last examined site. Scientists are hoping the rover’s batteries last that long. Enough to make the two kilometer trek. It will have to crawl out of its shallow position after which the rover is scheduled to search for more outcroppings of rocks to examine. An exploration that could help scientists add more information to their story of water on Mars.
At present the information gained is that the curb-height rock that Opportunity examined was once soaked with water as the scientists stated that the rock was infused with “enormous amounts” of salts. A condition that occurs here on Earth when the water evaporates leaving traces of salt inside rocks. Stephen Squyres, principal investigator for the Mars Exploration Rover from Cornell University, says that there are two case scenarios here. Either lots of pore space was created due to volcanic eruptions so that subsurface water seeped in or percolated in the pores or the reason could be a sea of salty water that once existed, evaporated leaving the settled salt and other sediments.
In each case, the environment had to be hospitable to life. Scientists are keener on the salty sea notion but Squyres is cautious and is not making any commitment to the theory of seawater or how long ago water might have existed. A geologist with the University of Colorado, Boulder, Bruce Jakosky, who helped to pick the rover landing sites, did offer some insight as to when the water might have existed. “Probably not the day before yesterday,” he states. But is of the opinion that water was present in the “early to middle Martian history, but there is a lot of wiggle room there, a lot of uncertainty”. Mars is the same age as Earth, approximately 4.5 billion years.
Opportunity must now start rolling beyond its landing site, the reason for which it was built, in order to understand the terrain in depth. Meridiani Planum is a windswept plain and before Opportunity roves up to it, two more interesting sites wait to be explored.
A rock called “Big Bend” and the “blue berry bowl” which is a small area in which there are several bluish round objects. These spheres can also be found sticking inside some rocks and their shape and existence have given scientists important insight into the water that was present in them. The composition of these layers though, is not known yet.
When Opportunity rolls out of its crater, it will examine the Haemetite deposits in the grains of the soil as the mineral usually forms when liquid water is present. There are larger deposits of the mineral in the plain above the landing site. Squyres feels that more crucial information is to be had in the next two weeks when the rover examines the plain. It will help understand whether water freely flowed in the area soaking the rocks or if it bubbled through the rocks. But he did admit that, “We may never know”. Thus the mystery might never unfold.
After the planned jaunt, Opportunity will aim towards “Endurance”, a crater 525 feet wide and thought to be the result of an asteroid impact in some distant past. But for Opportunity that will be a long journey. A 740-meter trip that may take several weeks. The rim of the crater has already been photographed by Opportunity and scientists are hopeful that it will be able to take a peek into the 100-foot deep crater, which according to Squyres “is going to be one heck of a view”. The anticipation is that the rim and the crater will have more extensive information material.
Joy Crisp, the rover project scientist at Nasa’s Jet Propulsion Laboratory, said, “we’re interested in finding out whether that bright rim material is the same as the outcrop or something different. It may have a different water story”. The team also feels that the rocks inside the crater might be older in origin. Opportunity will then, once again move 2 kilometers ahead to a mottled terrain south of “Endurance”.
But problems lurk there. The days are getting shorter as winter approaches and the sunlight that reaches the solar panels of the rover might not be enough. Moreover, dust collects on the panels, which limits the electricity that the rover generates. Though the craft has been designed to work through April but Squyres feels that it will outdo the time period by several weeks before its batteries die eventually. But it is presumed that the rover might not be able to make that trip south.
Spirit on the other hand (or the other side) is heading towards “Bonneville”, which is a crater inside a crater. If Spirit also detects a watery past inside the crater, then the Martian water story will be better understood as a wider picture of its past will develop.
Although, past evidence of water on the Red Planet does exist, as Jakosky, the geologist from the University of Colorado points out, “We know an awful lot about the history of water on Mars. There was liquid water on Mars. It was present in the crust at least in some places at some times. There’s reason to think it was widespread. We know substantial quantities of water have been lost to space”, this meaning that as the climate on the planet changed due to its gravity, which is 38 percent of Earth’s, the water disappeared into the atmosphere.
Even today some water vapour does remain in the Martian atmosphere, as water ice at the poles and underground at high latitudes. But does it come above the surface? And how does it cycle through the atmosphere? “We’re getting clues but we really don’t understand the basics yet,” said Jakosky.
Martian chemistry
One of the determining factors for Nasa regarding the presence of liquid water on the Martian surface is the presence of sulfates which are forms of salty chemical. At Opportunity’s location, lie particles compared to the size of blue berries in a microscopic image which has been taken from an outcrop of rock. These spheres don’t stick to the outside but are embedded in the layers of the rocks there and seem that they got stuck in there while the rocks we being formed. Opportunity’s Moessbauer spectrometer shows that jarosite, an iron-bearing mineral is present in the rock collection known as “El Capitan”, which is situated within the rocky inner edge of the crater it now resides in. A pair of yellow peaks in the image indicates jarosite. A phase in which water resides in the form of hydroxyl in the structure. The verdict; water driven processes do exist on Mars.
Specific instruments on Opportunity’s arm are being used in studying “El Capitan” in great detail and the panoramic camera helps in choosing the sites. The rock abrasion tool will drill the rock to find out more of the Martian rock chemistry. Opportunity’s microscopic imager located an interesting and puzzling object that looks like “Rotini Pasta”. Researchers both in the science team as well as outside are trying to figure out this strange formation and whether it has any interesting biology to be studied.
Opportunity’s studies of a rock outcrop earlier also came up with the sulfates. Steven Sqyures explains, “with this quantity of sulfates, you kind of have to have a lot of water involved”. Jarosite is the chief sulfate found. Cathryn Weitz, a program scientist with the MER (Mars Exploration Rover) program which also includes the Mars Express, stated, “on Earth, the only place we see this mineral is in areas where there is liquid water”. Jarosite, here on Earth is found in hot springs or acidic lakes according to her. Moreover, magnesium sulfate kieserite, also known as Epsom salt, including bromide salts on the Red Planet, indicate that it was green once. The minerals are both evaporite and exist on Earth where seas have known to have evaporated in time.
Remembering the lines from the famous poem “The Brook”, by Lord Alfred Tennyson:
Till last by Philip’s farm I flow
To join the brimming river,
For men may come and men may go,
But I go on for ever.
So goes the story of water on Mars. Though now just a trace of chemicals, water does have an unending story. One that “goes on for ever”. Today, when scientists say that they are now writing a book about the water on Mars, how far have they reached? “We’re writing Chapter One,” stated Jakosky. And mankind may one day learn that a wild stream on Mars did one day flow to join a “brimming river”.
The writer
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