The latest methane measurements on Mars to generate some intrigue among planetary scientists stems from the largest ever reading of the gas taken during the NASA Curiosity rover's seven-year mission, which again raises the prospect of microbial life existing at some time, some place on the Red Planet.

Because methane is a by-product of organic life on Earth, significant detections of it on other planets are noteworthy events in scientific circles. An example of a methane source here on our home planet are cows, but the gas can also arise from geological sources like volcanoes.

Whatever the reasons for methane on Mars, scientists are very interested to learn more. Hunting for methane is part of the Curiosity mission, and though it found nothing in the early days and dampened hopes of finding life on Mars, it soon began to pick up spikes in atmospheric methane, with one reading from 2013 measuring 15 parts per billion.

The latest and largest spike was picked up last week by NASA scientists, setting a new record for the mission at around 21 parts per billion. Methane doesn't tend to stick around in the atmosphere for too long, so detections such as this one are exciting as they suggest it was released in Mars' relatively recent history.

But where it is coming from is still very much unclear. Though there are currently no active volcanoes on Mars, it is possible that it is still arising from some kind of geological process, such as a chemical reaction between carbonate rocks, water and hydrogen. The Curiosity rover has no way of determining the source alone, but NASA plans to use data from follow-up experiments conducted over the weekend to shed further light on the discovery.

"While increased methane levels measured by Mars Curiosity are exciting, as possible indicators for life, it's important to remember this is an early science result," tweeted Thomas Zurbuchen, NASA's Associate Administrator for the Science Mission Directorate. "To maintain scientific integrity, the science team will continue to analyze the data before confirming results."

Source: NASA

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