He says the methane discovery presents scientists with a mystery because it is still not clear how the gas is being produced.

VOA: special.2009.12.30

Currently,the best explanation for the loss of methane is that it chemically reacts with dust in the atmosphere.

VOA: special.2009.12.30

In January,a team of NASA and university scientists announced that they had found methane gas on Mars.

VOA: special.2009.12.30

But Michael Meyer notes that methane also can come from a purely non-biological process called serpentinization.

VOA: special.2009.12.30

The gas is mainly methane. It produces half the carbon dioxide of other fossil fuels.

VOA: special.2009.10.23

This suggests processes that both supply and remove methane from the atmosphere in certain places.

VOA: special.2009.12.30

We also talk to a NASA expert about the discovery of methane gas on Mars.

VOA: special.2009.12.30

The orbiter could finally provide evidence about how methane on Mars is created and destroyed.

VOA: special.2009.12.30

Martian methane is also unusual because it is not evenly spread over the planet.

VOA: special.2009.12.30

For example,animal waste and cattle digestive systems release methane gas.

VOA: special.2010.01.05

On Earth,biological activity is very effective in making methane.

VOA: special.2009.12.30

Methane is better known as natural gas.

VOA: special.2009.12.30

He calls it "cow power to horsepower." Leonhardt says the challenge is to cost-effectively remove impurities from the manure-derived methane.

VOA: standard.2010.02.23

Manure from about 1,000 cows goes in one end and then, controlled decomposition yields methane gas at the other.

VOA: standard.2010.02.23