An unguarded remark by a Mars scientist working on the Curiosity mission has started a flurry of speculation that NASA has finally found signs of life on the Red Planet. The excitement is centred on samples of soil or rock that have been collected and analysed by one of the experiments on the mobile laboratory as it trundles around Gale Crater. 

Though he would not reveal what the findings were, Curiosity’s principal investigator John Grotzinger apparently told Joe Palca, of US radio network NPR: “This data is gonna be one for the history books. It’s looking really good.”

NASA are, wisely, still checking their data before they make any official announcement about what they have actually discovered. It is a process that is likely to take weeks though an announcement appears likely to be made at a gathering of the American Geophysical Union, in San Francisco from 3 – 7 December.

But the vacuum before that moment has inevitably been filled by rumours that it is some sort of compelling evidence that life is present, or more likely has at some time existed on Mars.

Curiosity, which landed on Mars in August and is more formally known as Mars Science Laboratory, will not have identified any martian bugs directly. It is not equipped to do so.

But it has a chemistry lab called SAM on board, short for the Sample Analysis at Mars experiment, that is designed to find the complex carbon compounds that are the building blocks of life.

Earlier this month, a first analysis of martian air by SAM proved disappointing for those eager for proof of aliens when it failed to detect any clear signs of methane that might offer further evidence of life.

Leading NASA scientist Carolyn Porco, a key figure in the Cassini probe’s exploration of Saturn, took to Twitter to caution: “Can I say something about this imminent announcement from Curiosity? A definitive discovery of organic compounds, if that’s what it is, does NOT meant that there are native organic compounds and therefore life on Mars. Organic materials are raining down on Mars all the time.”

Scientists have previously found organic materials in meteorites, boosting the idea that life on planets may have been seeded from space. However, they are not evidence of life in themselves.

Controversy still rages over whether more convincing signs including fossils of alien microbes have been detected in meteorites that fell to Earth after being ejected from Mars in asteroid impacts. Though some scientists including NASA experts support this finding, it is fair to say that the majority remain skeptical.

Another controversial suggestion is that NASA has already discovered evidence of life on Mars with its first Viking landers in 1976 but failed to recognise it.

Professor Dirk Schulze-Makuch, of Washington State University, looked again at the data and believes it indicates the presence of living alien microbes formed from a mix of water and hydrogen peroxide – hair bleach.

Unfortunately for those microbes, if they really did exist, they would have been either drowned or baked alive by the experiments that the Vikings carried aboard.