UPDATE 32: Actually, a quick link dump for further reading before we go: (1) the pictures and evidence that were shown by the scientists at the press conference; (2) The Daily Mail story on this; (3) and Reason magazine doing what Reason magazine does and explaining to you why not even water on Mars will save us from being doomed, doomed, doomed.

UPDATE 31: Press conference over. More information at the NASA homepage. So that does it for us too, except to reiterate how totally awesome that press conference was.

UPDATE 30: Last question, from a Nature reporter who is interested in the Science (rather than the last question, which was basically "how did it make you feel"). She wants to know how badly we've been messing up our Mars assumptions for a couple decades - unspoken: because this shouldn't be happening, based on what scientists have been thinking about the interior of Mars. Well played. The proposed solution is that the water is acidic, which causes a significant drop in the freezing point. Everyone laughs with relief.

UPDATE 29: Again, one of the scientists pops up with "it would be great if we had some money to go look at this very, very, very exciting stuff"

UPDATE 28: Three questions.
Q: Could you restate the general location?
A: Yeah, they're in the press release.

Q: How long would it take the moister to evaporate?
A: Dunno. Let me know when you figure it out.

Q: Is this how the original channeling (millions of years ago - that left evidence of oceans and rivers) happened?
A: No. These, as we said, are 10 swimming pools' worth. That is far less than an ocean (editor's note: slight paraphrasing, but really, not much).

UPDATE 27: Q: Where you happy when you made the most important astro-geological discovery of the last couple decades? A: Yes.

UPDATE 26: The question is about whether the models apply to NASA's plan (from yesterday) to colonize the moon. Answer: they've seen flashes from the moon that are almost certainly impacts, but they just don't know yet. But yeah, it'll probably be at least kind of a problem.

UPDATE 25: Excellent question about the models being developed for impacting objects. Why is this so important? The gut check for when you hear about water is "sweet - now we can colonize Mars". The gut check for when you hear about a high level of impacting objects is "well that sucks - no colonies for us". So it's a good news / bad news day for advocates of colonization.

UPDATE 24: Q: Can you estimate how often these features (of recent water flow) will show up in gullies? A: No - not a big enough sample size... but that does mean that it's pretty damn rare. But there are similarly light-toned marks in several other gullies. Unspoken: ... but, since they haven't observed changes in those gullies, they won't assert that it's water.

UPDATE 23: (1) "can you give a percent of how sure you are... are you 95% sure..."
(2) is finding water on Mars the holy grail of Mars exploration... what place does water occupy". Please excuse our elitism, but why do these people have jobs explaining anything to anyone?
Answers: That's not how exploratory science works, no percent for you. OH WOW. They are now LITERALLY MOCKING the "holy grail" question. Turns out, yes - water is important.

UPDATE 22: This scientist's respect for this reporter is so significant that he just literally reminded her that she lives in the Southwest US, just to make sure everyone is on the same page. He's now literally repeating the last explanation slowly, in an attempt to explain why a periodic burst of water flowing downhill is not like a geyser. Also - why water that is building up in a process of freezing is different than water that explodes by boiling. Because hot and cold are different.

UPDATE 21: The Los Angeles reporter has just asked if this is like Old Faithful. Sigh. We want to curl up and die. This is like 8 year olds asking the President about making laws.

UPDATE 20: An explanation of how it happens: "water is coming up from deep interiors... when it gets to the surface, it freezes, forming a dam... water keeps building up behind it, and it breaks the dam... there's a brief outflow of the dam ice ::giggle::... it picks up dirt, and flows downhill" - these are bursts of water running downhill, so they're not flowing right now. But they did flow on the surface, and they did it in the last few years. And they're reactivated from time to time.

UPDATE 19: It's incredible - they can find water on Mars, but they can't get a decent audio uplink across a couple of states.

UPDATE 18: Something like 20,000 gullies, and they only see the light-toned flows in only a tiny percent (but remember - the point is that in those gullies, they saw actual changes as they photographed it over a couple of times - it's water). Is it CO2 and not H2O? Maaaayyyybbbbeee - but you'd need pressure to get it under the ground, and for that you would need an atmosphere... and that doesn't seem likely at all.

UPDATE 17: "You can't see groundwater, because it's IN THE GROUND". If the Chron journalist didn't want to get talked down to, he shouldn't have suggested that the scientists were stupid for suggesting surface ice even though he couldn't see it in the pictures.

UPDATE 16: A suggestion that there are connections between the two big stories - water gets kicked up by the impact craters. But there are apparently all kinds of gullies being formed in all kinds of ways.

UPDATE 15: San Fran Chronicle Q: "how do you think this water is getting up there?" Answer: "yeah, we don't really know that". One of the interesting things about this conference, at least from a rhetoric of science standpoint, is the way that these scientists keep using phrases like "well, that's what science is all about". A little bit of Richard Dawkins-esque identity formation going on in the scientific community?

UPDATE 14: The critical point that makes this water (or rather, a mud flow) is that it went around pretty small objects, and it changed its pace like water would. And, again, you just don't find things that are this bright on Mars. It's water.

UPDATE 13: Haha - good for the scientist: "we already summarized this... they're very completely different".

UPDATE 12: Q & A - at this point, obviously, no new announcements. Just clarifications. NYT guy: "we've seen pictures similar to this before"... except this was clarified before... "how can we be so certain that this is a liquid flow". Or, in more plain speak, "can you write my science journalism column for me"

UPDATE 11: "Certain questions [about the water] still remain". We don't like this guy, Buzzkill. But: "we can honestly talk about liquid water on the surface of Mars TODAY". This is a HUGE day for NASA. Easily one of the most important in the last few decades.

UPDATE 10: They've got some guy on to explain why the other two guys before him are wrong.

UPDATE 9: They've explaining constant impacting objects on Mars as a reason why we should be very, very worried about getting hit by something very large. Maybe soon.

UPDATE 8: 100kiloton explosion, as one of 20 craters that they've found.

UPDATE 7: They've got two hi-res before/after shots of areas that were hit. "Beautiful" patterns of shockwaves and blast features. Awww... Giddy dorks. These people are really, really excited about what they've found. For good reasons.

UPDATE 6: SECOND huge announcement of today: watching the formation of impact craters, which are one of the best ways to get "under the surface" (literally) of a planet. They were watching the surface long enough to watch their formation. They're showing before / after pics.

UPDATE 5: "Five to ten swimming pools of water, coming down in each of the two cases". Also pointing out that if you were there, you'd want to get out of the way. "You'd be like, wow, there's this thing coming at me" -- NASA scientists are neat with words.

UPDATE 4: Is it frost? Wrong color. Salts or fine grains? Not so much.

UPDATE 3: "What is flowing... h2o is involved". They're ruling out everything else - dust, avalanches, etc. Water flowing down slope: it flows, it's got a light tone, etc.

UPDATE 2: They're showing pictures of gullies that have been changed by water within the last decade or so. WOW.

UPDATE 1: "no one expected what we have today. We have been able to image gullies over and over again... [we found] changes that indicate that materials had actually flowed through a gully... a liquid was involved"

Liquid water on Mars. Recently.

Go to the live feed and listen.

"We are talking about liquid water that is present on Mars right now"

Previously: People Smarter Than Us Roll Spirit Onto Mars, Producing Energy From Bubbles Is Neat, Science Illuminates Manuscripts