I want to leave headlines about fiscal cliffs, tragic shootings, apocalyptic warnings, and climate wake-up calls alone and focus instead on a story that received scant attention: NASA found life on Mars!
Well, not exactly. Scientists did announce, however, that they had discovered the essential element for life in a scoop of Martian soil, courtesy of the Curiosity explorer. The essential element is carbon, of course, and NASA found traces of it in the soil near where Curiosity made its landing back in August, in an area dubbed the ‘Rocknest.’
According to John Grotzinger, lead scientist for the mission, Curiosity ‘baked’ a soil sample in its microwave-sized oven discovering that it contained water, sulfur, and chlorine-containing compounds, including chlorinated methane gas – a substance that contains carbon. It didn’t, however, find these elements in sufficient quantity or in the right combination to create life. Still, the presence of carbon compounds in the soil sample was a bit of a surprise to the scientists. That’s because scientists aren’t sure where the compounds originated.
“We don’t know if they are indigenous to Mars or not,” Grotziner said. It’s possible that carbon molecules ‘hitched a ride’ from Earth as contaminants in Curiosity’s Sample Analysis on Mars laboratory despite careful precautions. It’s a situation similar to one that frustrated scientists during the Viking missions to Mars in 1977, when the two Viking rovers also scooped up Martian soil, heated it, and analyzed the gases that came off, detecting chlorinated methane. However, the Viking scientists eventually determined that the gas had been contaminated by solvents used to clean the rover before launch.
But Curiosity wasn’t cleaned with those solvents. And NASA performed its soil analyzing procedure four times with four different soil samples, only analyzing the fifth scoop when scientists felt confident that the threat of contamination was near zero. And voila! Chlorinated methane gas! Carbon on Mars!
According to Paul Mahaffy of NASA, what Curiosity detected were trace amounts of three of the simplest possible carbon-containing compounds: a carbon atom with one, two, or three chlorine atoms attached in place of hydrogen atoms. The heating, he said, may have decomposed a natural component of Martian soil which in turn could have broken down some form of carbon in the soil sample and chlorinated its carbon atoms. The next step will be to determine whether the carbon in the Martian soil was abiotic – a non-living chemical or physical process – possibly the result of the presence of carbonates, such as the baking soda in your kitchen cupboard, or whether it was biotic – the result of a biological process – such as the impact of a hydrocarbon-bearing asteroid that landed recently or the remains of a living microbe or other organism that died a long, long time ago.
However, just finding carbon doesn’t mean that you’ve found life. “If you have organic carbon and you don’t have any water, you don’t have a habitable environment,” said John Grotzinger. Even with carbon and water, life needs other chemicals, such as sulfur, oxygen, phosphorous and nitrogen, to form and evolve. “It tells us that we have a lead into a measurement of one of the important ingredients that adds to a habitable environment,” Grotzinger said. “We still have a lot of work to do to qualify and characterize what it is.”
In the meantime, here’s a photo of the scoop:
Another condition for life is water, and once upon a time, Mars had a lot of water.
In 2004, NASA’s rover Opportunity discovered evidence that long, long ago Mars was once a wet planet, raising hopes that evidence of past life could be found today. In the same year, NASA’s Mars Explorer detected huge reserves of water ice at the planet’s south pole, followed a year later by an announcement that water also existed at the north pole. In 2006, NASA displayed images taken by the Mars Global Surveyor which suggested water had flowed on the surface of Mars fairly recently, though some scientists were skeptical, suggesting that sand or blowing dust could produce similar effects. In 2008, NASA’s Phoenix rover, which landed in Mars’ Arctic plain, confirmed the presence of frozen water below the surface when it exposed water ice while digging into the soil. After four days, the water was gone – sublimated back into the atmosphere.
Today, scientists are very confident that Mars had abundant water very early in its history. Snow and rain fell on the planet, creating rivers, lakes, and possibly oceans, evidence by the presence of large clay deposits. Life may have happened as a result of all this water (plus carbon in the soil) – which is why NASA is still digging holes in the Martian soil. NASA would also like to understand in better detail what happened to Mars over the millennia. Nearly all of the water eventually disappeared, the atmosphere became composed mostly of carbon dioxide, temperatures plummeted, and life – if it ever existed – was extinguished. In other words, Mars experienced a profound change in its climate, likely the result of intense volcanic activity which may have released large amounts of carbon dioxide into the atmosphere. In this case, Mars went through a massive case of global cooling, not warming.
As they say, more research is needed.
By the way, in September, NASA reported “clear evidence” of carbon dioxide snow at Mars’ poles – the only known example of carbon dioxide snow falling anywhere in the solar system. Frozen carbon dioxide – known as ‘dry ice’ here on Earth – requires temperatures of about -193 F. NASA said the carbon dioxide snow reminds scientists that although some parts of Mars may look quite Earth-like, the Red Planet is a very, very different place.
Here is a picture of water erosion on Mars, courtesy of Curiosity. Look familiar?