If Martian life survived from its wet past dating back 3 billion years, it is nowhere to be found on or near the surface today. The Meridiani Planum meteorites were first examined by Opportunity, the surviving Martian rover that was part of a twin set that arrived on Mars over 12 years ago. Opportunity in its journey to Victoria Crater found meteorite fragments seen below in the false colour image. The meteorites stand out from surrounding landscape and provide a good reference point for studying chemical weathering on the planet’s surface.
The weathering of the ferric iron content as analyzed by Opportunity’s on board spectrometer, has been compared to similar meteorites collected from Earth environments. On Earth chemical weathering rates in Antarctica are slower than anywhere else on Earth. But on Mars evidence shows that weathering is 4 orders of magnitude slower than Antarctica. In fact the weathering of Martian meteorites shows no evidence for liquid water within the chemical process.
The existence of water has been found by Curiosity, the other operating rover studying conditions in Gale Crater. It observes seasonal changes to relative humidity close to the Martian surface with the formation of salty brines containing perchlorates within the top 5 centimeters (2 inches) of the planet’s soil. But the moisture levels observed are far less than that found on Earth’s driest places.
The Spirit rover had made similar observations when studying Gusev Crater. In fact the rover’s demise was caused probably by its wheels breaking through a soil crust in a small crater. Operators of Spirit surmise that the crust formed from evaporated salty brine that hid the sand beneath.
Getting back to the Meridiani meteorites and what they tell us about current Martian surface conditions, indicates that Mars appears to be in an interglacial period experiencing very dry conditions in equatorial regions of the planet. The extreme aridity is 4 orders of magnitude greater than the driest place on Earth. It is highly unlikely, therefore, that Martian life can exist in these areas where current Martian explorations have taken us.
Dr Christian Schröder, Lecturer in Environmental Science and Planetary Exploration at University of Stirling, a principal member of the research team that produced the above-mentioned paper, states, “Evidence shows that more than 3 billion years ago Mars was wet and habitable. However, this latest research reaffirms just how dry the environment is today. For life to exist in the areas we investigated, it would need to find pockets far beneath the surface, located away from the dryness and radiation present on the ground.”
]]>Over the winter the rover rested in one spot trying to maximize the charge in its lithium-ion batteries. It chose its stop well because the Martian winds dusted off the solar panels that power it up. Prior to parking for the winter Opportunity’s solar panels were down to 60% efficiency. But the wind cleared the dust and now the rover is cleaner than it has been since 2005 and is converting solar energy with better than 70% efficiency. That’s generating 615 watt hours. The rover needs only 100 watt hours to operate so the lithium-ion batteries should be kept fully charged with all this extra energy to spare.
Now the rover is on a new mission to climb a nearby ridge of hills that have been named Murray Ridge. One particular area along the ridge, called Cape Tribulation (seen in the postcard image below) is of particular interest because of its unusual rock formations. The Opportunity Jet Propulsion Laboratory team on Earth believes these rocks bear the signs of a prior Martian wet period. Opportunity has already made discoveries that suggest Mars in the past experienced periods that may have been life-friendly. The trek to Cape Tribulation is expected to take two years.
From time to time Opportunity takes a selfie using its panoramic camera. It took one back in January when the rover’s solar panels were covered in dust. That’s the picture seen below on the left. The latest picture from April on the right shows how the winds of Mars have brought a new shine to the rover’s solar array and given it some additional oomph.
In the second decade of the 21st century Mars is more a puzzle than understood. The question our Martian adventure is getting close to answering is this: Is Earth the sole planet where living things exist? And we are getting closer to this answer without ever setting a human foot on the planet’s surface. Instead our Martian studies have involved a series of robotic missions loaded with scientific instruments. These missions have included orbiters, robotic landers and rovers. The information we have gleaned from these incredible machines has painted a picture of Mars that is altering our perspective of what constitutes a planet capable of harboring life. Let’s look at some of the technology that has gotten us to this point.
From Odyssey to Spirit and Opportunity
Odyssey
Aptly named Mars Odyssey after Arthur C. Clarke’s novel, 2001: A Space Odyssey, NASA launched this robotic mission to the planet in April 2001. Its primary mission focused on studying the Martian atmosphere, surface and subsurface using three scientific instrument packages named THEMIS, MARIE and GRS. THEMIS was designed to study active thermal occurrences on the Martian surface in order to detect surface minerals by their spectral fingerprint. MARIE was designed to study the radiation from cosmic rays not only in the vicinity and surface of the planet but throughout the interplanetary space between Earth and Mars. GRS was designed to study Martian chemistry using gamma ray and neutron detectors. Odyssey arrived at Mars in October 2001 and entered orbit on the 24th. Its original mission was designed to end in August 2004. The spacecraft continues to operate on an extended mission more than a decade after its arrival.
The Odyssey mission has given us a better picture of both the planet and what a human mission would experience in travelling there. The results of MARIE sampling indicates that humans travelling between Earth and Mars would experience twice as much exposure to cosmic rays as humans on the International Space Station.
We also have learned from THEMIS that Mars polar ice caps unleash gas jets of CO2 every spring, that the Martian surface has extensive chloride salt deposits left behind when large bodies of liquid water evaporated, that the atmosphere can churn up dust storms and dust devils similar to those found in deserts on Earth, that at least one large crater, Aram Chaos, was once a lake, and that the planet has extensive water-eroded channels on its surface. From GRS data we have detected evidence of substantial subsurface ice as well as deposits of iron, silicon and potassium.
Spirit and Opportunity
In 2004 two robotic spacecraft arrived on the surface of Mars to deploy two rovers, Spirit and Opportunity. The mission for both rovers packed with scientific instruments was to last 90 days with the objective to explore the Martian terrain, study its geology, look for evidence of water in the past and present and relay images back to Earth receiving stations. Solar power and batteries have provided the power to all the instrumentation and cameras.
Deployed at landing sites on opposite sides of the planet both rovers exceeded expectations with Spirit the first to succumb to the harsh Martian environment as it became trapped in soft Martian terrain in spring of 2009, eventually falling silent during the winter of 2010.
Opportunity, however, continues to chug along as of May 2012, a remarkable feat of technological engineering supported by a dedicated team of Earth based scientists who continue to devise new experiments and missions for the rover.
What both Spirit and Opportunity discovered shortly after landing included significant evidence that Mars was once a wet environment and that the evidence in the rocks shows that the planet has experienced wet and dry periods throughout its geological history. While on the Martian surface Opportunity has far outpaced its sister rover, Spirit (7.7 kilometers or 4.8 miles before getting stuck) accumulating a total driving distance of 34.4 kilometers (21.4 miles). To experience a portion of Opportunity’s remarkable journey access the video created by the science support team’s piecing together of end-of-day images taken by the rover as it travelled almost 21 kilometers (13 miles) between the Victoria and Endeavour Craters on the planet’s surface.
Opportunity’s current location is on the edge of Endeavour Crater assignment where it is hunkered down in its fifth Martian winter. Acting as a stationary observation platform it is conducting a study of the interior of the planet using radio-tracking to measure any wobbles as the planet rotates. A significant wobble will indicate whether Mars has a molten core or not. As Martian spring and summer unfold Opportunity will resume its trek, an amazing accomplishment.
The story of our exploration of Mars will continue in our next Space and Humanity in the 21st Century blog.
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