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Confirmed: Water Once Flowed On Mars
An anonymous reader writes "A new study based on observations last September by the Curiosity rover on Mars has confirmed that pebble-containing slabs of rock found on the Martian surface were part of an ancient streambed. The work provides some of the most definitive evidence yet that water once flowed on Mars. '[The pebbles'] smooth appearance is identical to gravels found in rivers on Earth. Rock fragments that bounce along the bottom of a stream of water will have their edges knocked off, and when these pebbles finally come to rest they will often align in a characteristic overlapping fashion. ...It is confirmation that water has played its part in sculpting not only this huge equatorial bowl but by implication many of the other landforms seen on the planet.' According to NASA, 'The stream carried the gravels at least a few miles, or kilometers, the researchers estimated. The atmosphere of modern Mars is too thin to make a sustained stream flow of water possible, though the planet holds large quantities of water ice. Several types of evidence have indicated that ancient Mars had diverse environments with liquid water. However, none but these rocks found by Curiosity could provide the type of stream flow information published this week. Curiosity's images of conglomerate rocks indicate that atmospheric conditions at Gale Crater once enabled the flow of liquid water on the Martian surface.'"
I realize I could easily look it up. But, what is the leading theory as to why the planet can no longer sustain liquid water. I know that in it's current condition with low gravity and lack of atmosphere it cannot sustain liquid water... But was Mars once larger?
Runaway atmosphere loss is a leading candidate due to a lack of a magnetic field (and those missing gigatons of rock)...
The thick crustal material and low magnetic field have led to the loss of the atmosphere and lack of currently flowing water. Low magnetic field led to large impingement by solar wind and stripping of atmosphere. Low average density of planet let atmosphere escape. The thick crust has kept the mantle deep and there is no regeneration of gases and liquids from the interior. Low atmosphere, more radiational cooling and first water goes to ice and then CO2 goes to ice and reduces the atmosphere again. The Earth could have gone the same route, had an impact not spawned the moon and thined the planet of the lighter, thicker crustal material. Lots of imparted spin from the impact and a denser planet gets deep iron core spin to generate a protective magentic field. That field both protects the atmosphere and the biologicals from getting zapped. Would be fun to send lots of water and gas bearing comets to impact and terraform Mars, but it would all still leak out. So --- we are seeing prehistoric water, frozen in time,and relected by the rounded pebbles left behind in ancient Martian canals.
Extremely hot or cold liquids would have done more to the pebbles than just knock their edges off - we can figure pretty well that they weren't melted or supercooled. The simplest conclusion for "liquid that flows in streams at the temperature range in question" would be either "water" or "the blood of thine enemies".
Everything is better with chainsaws.
There are few other candidate liquids. We know Mars has water ice. We've detected liquid methane elsewhere in the solar system, but Mars is too warm to support liquid methane. Liquid CO2 is unlikely because at Mars' current temperatures, you would need more than one Earth atmosphere of pressure to form a liquid, and a thicker atmosphere will usually mean a warmer planet.
Nope, flowed is a past tense of flow, flown is a past tense of fly.
Which is why I long ago gave up correcting non-native speakers of English, and have discovered that sometimes garbled English is actually far more expressive and accurate than 'proper' English.
Some of the best puns I've heard are grammatically incorrect, but completely on-point in context.
Flew is the past tense of fly, flown is the past participle.
I disagree. The prevailing theory is that solar wind tore at the atmosphere gradually due to the lack of a magnetosphere.
This itself accounts for all of the loss. In fact, it is a bit hard to explain how Mars did actually maintain an atmosphere for as long as it appears to have. Perhaps it has a weak magnetosphere in the past...
There is an impact crater that's pretty massive, but Earth has several of those too...