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Mars Orbiter Finds Evidence For Ancient Rivers, Lakes
Cowards Anonymous points out news that studies based on data from the Mars Reconnaissance Orbiter have found that vast regions of Mars contained rivers and lakes when the planet was young. The studies also suggest that the water existed for quite some time, often in standing pools, which are conducive to the formation of basic organic matter. NASA provides a color-enhanced photo of a delta within a crater. Quoting:
"The clay-like minerals, called phyllosilicates, preserve a record of the interaction of water with rocks dating back to what is called the Noachian period of Mars' history, approximately 4.6 billion to 3.8 billion years ago. This period corresponds to the earliest years of the solar system, when Earth, the moon and Mars sustained a cosmic bombardment by comets and asteroids. Rocks of this age have largely been destroyed on Earth by plate tectonics. They are preserved on the moon, but were never exposed to liquid water. The phyllosilicate-containing rocks on Mars preserve a unique record of liquid water environments possibly suitable for life in the early solar system."
They had plenty of greenhouse gases. The problem was that after the geomagnetic field of Mars was lost, the solar wind was able to strip away the atmosphere, leaving it today at about 5 to 10 millibars (in contrast with the Earth which is about 1000 millibars).
"'scuse me, 'scuse me, officer JPLNazi coming though... "
...vast regions of Mars contained rivers and lakes...
This has been OLD NEWS since the Viking orbiters, more than thirty years ago, though thanks to the demands of the mass media, the goldfish-like attention spans of the general public and the rigours of academic tenure, publishing, and funding rounds (not to mention PR teams at academic institutions, who often seem to know jack shit about the subject they're writing a press release on) it gets recycled every time there's a water-related Mars discovery. I'm sure I've seen three or four water-related stories based on MER (rover) research, then there's the Mars Express data, Mars Odyssey's spectrometer data (hint: why do you think Phoenix happened to land somewhere where there's water ice 5cm below the surface - luck?). Oh yeah and of course Phoenix is just about to drop ice scrapings into the TEGA oven and cook out any water, carbonates, in fact everything else that vaporises at less than 1000 degrees C.
The significant aspects of the two new papers (one in Nature, on in Nature Geoscience) are indeed the phyllosilicates, more commonly known as clay minerals. (if you're thinking of the clay in your back garden, imagine it after lying in an Antarctic dry valley for a three plus billion years, in a near vacuum, and hammered with UV. To the layperson this is what Arthur Dent would have identified thusly: "well, it's rock, isn't it?" It adds to the evidence for medium-term (up to 10^6 years) periods of free-standing or flowing water on the surface at essentially every scale, from regional morphology such as flash flood outflow channels, river deltas, coastlines and the like down to rock formations that are clearly indurated, contain silica minerals (google 'Spirit Tyrone') or haematite (blueberries, which are concretions formed in water-saturated rocks) and vugs (voids left by water-soluble crystals.) When you wet particular kinds of rocks that Mars is known to have a lot of, you get clays (phyllosilicates) as a result.
By the way the NASA image isn't
"colour enhanced"
-- that's CRISM data overlaid on a visible-wavelengths image. (CRISM is a spectrometer and is the instrument that ID'd these minerals.)
...standing pools, which are conducive to the formation of basic organic matter.
This statement is, uh, mistaken. What it's getting at is the notion that long periods of exposure to water is generally considered to be probably very very important if not essential to early life. ("organic matter" would be anything with a carbon atom in it, e.g. coal, plastic, methane, oil... it's one of those words that means something totally different in particular scientific context. Like "metals" (tho' that means at leat three different things to different sciences...)
Much much more at a popular search engine near you.
Martian geological time is subdivided into a number of time periods based upon major geomorphological features seen from orbit -- major crater basins, the density of craters (generally speaking, crater frequency was higher in the deep past -- as on the Earth's Moon), canyons and channels such as Valles Marinaris, and volcanoes. While it isn't possible to determine their exact numerical age, it is possible to figure out their relative age (i.e. the order of the events that made them). For example, the overlapping shapes of craters tells you which impact formed first. If a volcano has a crater on it, then obviously the volcano formed first and then the crater. If a channel is eroded into a crater, then the channel came after. That kind of thing. So, there's a reasonably detailed relative chronology for events on Mars, and this is divided into eras known as (from oldest to youngest) the Noachian, the Hesperian, and the Amazonian.
Using crater densities and the fact that rocks were recovered and dated on the Moon, it is possible to link the better-known chronology of the Moon to that of Mars. There are significant uncertainties of course, but generally speaking that allows people to estimate that the Noachian was from about 4.6 billion to about 3.5 billion years ago, essentially the time when the cratering frequency started to drop off on the Moon. There is ample evidence that at this time on Mars there was freely-flowing water on the surface, hence, "Noachian".
The pages cited above has some really nice charts and descriptions, and the wikipedia page has a map showing the distribution of the deposits of different ages.
but the fact that Venus has no signs of life proofs that women do not really exist and are just the results of a fevered imagination. This handily explains why slashdot, a bastion of clear thinking, has no women.
MMO Quests are like orgasms:
You may solo them, I prefer them in a group.