They seem to have discovered methane on Mars.

I find this much more exciting than water for two reasons. First, while there are abiological means of methane production (e.g., vulcanism), if there's been any recent (i.e., in the past few hundred years) such activity, this would be the first and only evidence of it, so some form of life is definitely a strong possibility. Water means that life might have once been there. Methane means much more strongly that it might be there now, since it doesn't persist that long.

It's also potentially a source of fuel, though it may be too trace to easily collect.

[Hat tip to "cspackler" at Free Republic, from an amusing thread on this topic.]

[Update a couple minutes later]

The best place to go for in-depth and smart blogging on subjects Martian is probably Oliver Morton's Mainly Martian site. He's all over this one, and has taken the effort to come up with flatulent cow equivalents. He thinks it's just a couple thousand for the whole planet.

You beat me to mentioning Oliver Morton's blogsite on this. Morton notes that there are at least three explanations for the methane: life, volcanism, and meteorites delivering organic materials to the atmosphere.

Morton actually posted this info several weeks ago almost as an aside. I cannot find that original post, but if anybody deserves credit for breaking the story, he does.

I'm glad cspakler got the thread published here. We've got some dang funny folk in FReeper land.

I think he has linked with each of the previous stories when he's done the subsequent "installments".

This is what he calls the first post on the subject, a check in the archives in February didn't turn up anything earlier than this:

http://mainlymartian.blogs.com/semijournal/2004/03/methane_and_thu.html

Regarding Morton's first post on the methane, yeah, that's what I found. I simply remember seeing mention of Martian methane on his website at least a few weeks ago. My memory could be wrong, but it just seems odd. When the stories started coming out I remember thinking "well, Morton mentioned that awhile ago, didn't he?"

I guess I could ask him directly.

"Further observations and analysis showed that ethane and methane each constitute about one percent of the frozen gases in Comet Hyakutake. (The astronomers measured radiation from gases released from their frozen state as the solid nucleus -- or "dirty iceball" -- of the comet was warmed by the Sun.)"
http://stardust.jpl.nasa.gov/news/r96-108.html

"Kerr mentions two possibilities; volcanic activity or bacteria. Methane in the atmosphere suggests that one or other of these processes is going on now. (A third possibility comes from above, not below: the recent impact of a comet, since comets contain methane. But there doesn't seem to be any sign of the very fesh looking crater that would be associated with such an event in any of the datasets, and it seems unlikely that a comet small enough to be destroyed by Mars's thin atmosphere, and thus not leave a crater, would be big enough to leave a global methane signature for any length of time.)"
http://mainlymartian.blogs.com/semijournal/2004/03/methane_and_thu.html

I would say that the Earth receives thousands of tons of material from space each year- without leaving impact craters. Mars would also receive thousands of tons without leaving "noticable" impact craters. Because of Earth's dense atmosphere we receive less craters per year on average than Mars would- it is a certainty that there is new craters on Mars- if new means in the scale of hundreds of years, the crater sizes tens of meters & up. They may not be noticeable, but that is only because we haven't looked at Mars at the level of resolution needed and for long enough period of time for it to be noticeable. [Remember at 5-10 meter resolution that's a few pixels]. I would think a conservative guess is that Earth recieves tons of methane per year from space- not as an average- but say last year and the year before that- typical and constant minium. And though a smaller planet, Mars because of it's location, could recieve around the same or more methane. Now, to reach 240 tons per year, this could be much more than the normal rain of methane space- but you could have one large impact delivering 1000's of tons of methane or several adding hundreds of tons, or say a near miss of a comet and/or yearly pass through it's trail.
Therefore at least a small portion of the methane detected on Mars comes from Space, and it's possible that say 1/2 or all is coming from Space.

FWIW, the first mention of methane on mainlymartian was back in early March, here -- I talked about the possibility of methane warming early mars, and Bruce Moomaw mentioned Michael Mumma's work in the comments.