Guide to the Cosmos

Making the Wonders of our Universe Accessible to Everyone


     Newsletter: Mars Curiosity Update


Since it’s spectacular landing on August 6, 2012, the NASA/JPL Curiosity rover has been exploring Mars for 18 months. Curiosity had traveled over 3 miles and witnessed 550 sunrises. While no little green men have come forth to greet it, so far, Curiosity has found evidence that life could have existed on Mars billions of years ago. But it has also shown that the search for definitive evidence of extraterrestrial life may require decades of additional exploration.



NASA’s exploration of Mars began 50 years ago with Mariner 4’s successful 1964 flyby.


Seven years later, on November 14, 1971, NASA’s Mariner 9 became the first space mission to orbit another world by overtaking the Soviets’ Mars 2 orbiter, which launched 11 days earlier but arrived 13 days later.


NASA’s Viking 1 made the first successful Mars landing in 1975, and survived for 2245 Martian days, which scientists call “sols”.


In 1997, NASA’s Sojourner became the first vehicle to drive on Mars.


Seven years later, NASA landed larger rovers, Spirit and Opportunity; the latter is still operational after 10 Earth years.


JPL scientists amongst duplicate Mars rovers from each generation


JPL, a division of Caltech, designed, built, and operated all these NASA missions. To date, no other nation has successfully landed a spacecraft on Mars.


Spirit and Opportunity proved liquid water had once existed on Mars, at least sporadically. Water is a favorable solution for biochemical reactions, and it provides two vital elements: hydrogen and oxygen. But, a habitable environment requires much more. Life also requires the availability of several other elements, an energy source, and a chemical environment free of extreme acidity, alkalinity, or salinity.


Curiosity’s most important discoveries, according to NASA, are finding:

·      habitats suitable for life

·      stream beds of ancient rivers

·      an unexpected diversity of environments

·      an absence of methane

·      and perilous radiation levels


Let’s discuss these further.


Curiosity has shown that habitable conditions once existed, at least briefly in some limited areas. It found all of life’s most essential elements: hydrogen, carbon, oxygen, nitrogen, phosphorous, and sulfur. Curiosity also found locations with favorable chemistry and energy sources. Such favorable conditions, which are rare on Mars, might have been adequate for microbial life. No serious scientist still believes that advanced life forms ever existed on Mars.


One possible Eden has been imaginatively named Sheepbed in Yellowknife Bay (it has no sheep, water, or knives). Clay minerals there suggest abundant water with neutral pH and low salinity existed billions of years ago. Radioisotope analysis shows that the surface here has been exposed to cosmic and solar radiation for only 50 to 110 million years. It may have been deeply buried billions of years ago, and recently exposed by wind-driven erosion. Also present are minerals with a variety of oxidation states that microbes could have exploited for chemical energy. A paper by JPL scientists led by Caltech Professor of Geology John Grotzinger estimates that liquid water existed here for between hundreds of years and tens of thousands of years. If what we now see was just part of a much thicker deposit, this area could have been habitable for much longer. By comparison, the origin of life on Earth is generally believed to have taken hundreds of millions of years. 


Curiosity found that methane, a signature of most life forms, is conspicuously absent from the Martian atmosphere. Less than 20 tons of methane per year are entering Mars’ atmosphere — 50 million times less than on Earth — diminishing the possibility of current or geologically recent life.


Radiation levels at Mars’ surface, as measured by Curiosity, are much higher than some hoped. Mars lacks both Earth’s robust atmosphere and magnetic field, which greatly reduce our radiation exposure. Any future manned missions to Mars will require massive shielding.


Curiosity was designed to search for habitats suitable for life, but isn’t equipped to search for evidence of life itself. Curiosity has shown that such evidence would rapidly decompose at or near the surface. Future Mars missions must target ancient aqueous environs that were deeply buried billions of years ago (when there was water) and were recently exposed. This will be a severe challenge. Earth is far more benign. Thousands of scientists have scoured Earth for over 100 years, searching for signs of ancient microbial life, and yet the evidence remains debatable. The odds seem daunting that one robot could find compelling evidence within one tiny part of a more hostile planet 100 million miles away.


Yet, Mars is our best chance to find life beyond Earth.


Best Regards,



Feb 26th, 2014