Hello it's Howard in London with a special edition, a short one of the unexplained just to bring you up to date with the developments announced by NASA in the last few days to do with Mars.

What you're about to hear is an interview with our space specialist Nick Lister from astronomy for all.co.uk explaining it all.

This will be broadcast on my radio show on Sunday night June 10th, but I wanted you to hear this here now.

As you will have heard on Thursday, certainly in the newspapers on Friday, NASA, after a lot of news coverage about the announcement of the news conference held a news conference involving some of its top scientists and a supposed announcement about the discovery of something on Mars.

Of course that got the speculation machine running in top gear and a lot of people saying could this be it, could it be life on Mars.

And the truth is what they've come out with is a possible step along the way to that discovery.

The way that it's been reported Friday morning curiosity rover has uncovered the best evidence yet that life may have once existed on Mars.

Two separate studies on data collected by the curiosity rover over the last few years have brought scientists to identify an abundant source of organic matter in an ancient lake bed.

And they've traced some of the planet's atmospheric methane to its roots. So two important studies, the organic matter in the lake bed and the methane, where's that coming from and why does it appear to be seasonal.

Let's hear first of all from Chris Webster at NASA's JPL lab in Pasadena California.

We've seen the seasonal variation and we've tried to look at the data and come up with some explanations and we've been able to rule out some of the some of the sources.

We don't actually think the meteoritic or delivery of interplanetary dust that can produce methane in the atmosphere as Jen said.

We don't think that's so important because we wouldn't expect to see a large seasonal variation. We might see 20%.

Instead, we're seeing this massive change in the methane signal.

And so what we consider, we look at the data and the idea that best fits our data is the idea of subsurface storage.

So way under the ground, under Mars, there's methane that's trapped. It may be trapped as clathrates or other materials.

We don't know if that methane is ancient. We don't know if it's modern. It could be either.

And we also don't know if that methane was created from water rock chemistry like serpentinization or it was created by a methanogen microbes.

We cannot distinguish that. So, but the methane leaks or seeps up to the surface, we believe, and finds its way through cracks and fishers.

And eventually when it gets to the surface, we're then in a situation where the surface temperature can modulate or especially amplify the release of methane.

So this is an exciting time because we have this seasonal cycle to constrain some of the theories and of the sources and things of this important guess.

Now, Chris, I want to talk to you a bit more about trying to distinguish between whether this is a biological or non-biological source of the methane.

...