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Mars Gullies Show Water Once Flowed
NewYorkCountryLawyer writes "A new analysis of puzzling gullylike features on Mars offers further evidence that water flowed on the Red Planet's surface, perhaps as recently as several hundred thousand years ago. The findings bolster the case that melting snow from a departed Martian ice age carved these gullies, rather than shifting sands or other 'dry' phenomena."
Our combination of gravity, temperature and magnetic field strength means there is negligible loss to the atmosphere even over massive time-scales.
Thankfully.
Would be excited to hear if underground water is found. The ice caps probably don't have the volume to fill what potentially could have been an Earth-ish looking planet.
They wouldn't need to. Mars has only about a third of the surface area of Earth. Which makes for a nice coincidence as we both have roughly the same available landmass!
It is dangerous to be right when the government is wrong.
Mars's biggest problem is gravity.
The molecules in a gas move at rather high velocities (you can calculate this with a Maxwell-Boltzmann distribution). If some of those molecules are moving faster than escape velocity, they may simply fly off into space. Over time, unless the atmosphere is constantly being renewed (from volcanic eruptions, etc.), the planet will become a bare rock.
Not all gases disperse at the same rate, mind you. A mixture of gases tends to exist at a common temperature. And temperature is a measure of kinetic energy, a product of both mass and velocity. In other words, light atoms and molecules move more quickly, and massive atoms and molecules move more slowly. Planets with low escape velocity can only retain heavy, slow moving molecules. Planets with high escape velocity can retain lighter, faster atoms and molecules. This is why large planets can have atmospheres composed of the lightest elements (hydrogen, helium), while small planets and moons have no atmosphere or are limited to heavier molecules (like hydrocarbons).
Fortunately, the Earth is massive enough that it loses its primary atmospheric gases (nitrogen and oxygen) very slowly, and any small losses can be replaced by outgassing from the surface. However, smaller, faster atoms and molecules like hydrogen and helium still escape.
Mars, on the other hand, is far lighter than the earth and cannot retain an atmosphere nearly as well. Mars also has no magnetic field or ozone layer, so the atmosphere is subject to high-energy solar radiation. This radiation both adds heat and breaks molecules apart, speeding them up and "helping" them escape the gravity well. Over time, it's likely that whatever atmosphere Mars had created during its volcanic period simply dispersed.
How can I believe you when you tell me what I don't want to hear?
This hapenned supposedly when Mars had an active nucleus that generated a magnetic field, protecting the atmosphere from solar winds.
Nowadays liquid water cannot exist on Mars surface, and the bigger mistery is why Mars lost it's magnetic field.
It lost its magnetic field as the core cooled. The fluid movement of a metallic core is what generates Earth's magnetic field.
Hi NYCL, the summary (TFS) should have been written as: "Lest there be any doubt that Brown University's Planetary Geosciences Group graduates Samuel C. Schon, James W. Head, and Caleb I. Fassett, study authors, NASA Martian crater dating, really do 'get it' about the presence of water in recent Mars history, all such doubt should be removed by the paper his team just released (http://geology.gsapubs.org - March 2009, either slashdotted or slow). It shows the Martian gully system is craterless, possibly as young as 1.25 million years old (see bottom right of photo). In the paper lead study author Schon spells out, in the clearest possible terms so that there can be no misunderstanding, that at the extraordinary HiRISE (High Resolution Imaging Science Experiment) image taken by the Mars Reconnaissance Orbiter ...
:)
(For those of you who don't know what Troll8901 is getting at... he's mocking me, referring to this)
Ray Beckerman +5 Insightful