Astronomy Picture of the Day - powered by LUNEXIT.IT

Today's APOD shows us some interesting Surface Features found on the Floor of an Unnamed Crater, located to the East of Aram Chaos and Ares Vallis. As you can see, there are two distinct elevations on the Crater Floor, which may indicate the presence of Layered Fill Material. Aram Chaos (that is centered at 2,6° North Lat. and 21,5° West Long.), is believed to be the visible remnant of an extremely ancient - and therefore heavily eroded - Impact Crater. It lies at the Eastern End of the large Valles Marineris Canyon System and close to the Outflow Channel known as Ares Vallis. Various geological processes have reduced it to a circular area of Chaotic Terrain. Aram Chaos takes its name from Aram, one of the Classical Martian Albedo Features observed by Giovanni Schiaparelli, who named it after the Biblical land of Aram. Aram Chaos measures about 280 Kilometers (approx. 170 miles) across, and lies in a Region called Margaritifer Terra, where many water-carved Channels show that Floods poured out of the Southern Highlands onto the Northern Lowlands ages ago. The Thermal Emission Imaging System (THEMIS) onboard the NASA - Mars Odyssey Orbiter found Gray Crystalline Hematite on the Floor of Aram Chaos, while the CRISM - such as the Spectroscope onboard the NASA - Mars Reconnaissance Orbiter -, found Hyrdrated Sulfates, Jarosite and, again, Hematite.

Hematite is an Iron-Oxide Mineral that can precipitate when Groundwater circulates through Iron-rich Rocks, whether at normal temperatures or in hot springs. The Floor of Aram Chaos contains huge blocks of collapsed, or chaotic, terrain that formed when Water and/or Ice were suddenly and catastrophically removed. Elsewhere on Mars, the release of Groundwater produced massive Floods that carved large Channels like Ares Vallis as well as other similar Outflow Features. In Aram Chaos, however, the released water stayed mostly within the Crater's Ramparts, eroding only a small, shallow Outlet Channel in the Eastern Wall. The presence, within Aram Chaos, of several elements that require water to form - including Hematite, Sulfate Minerals, and water-altered Silicates - suggest that a large Lake probably once existed within the Region.

Ares Vallis instead, is an Outflow Channel which appears to have been carved by fluids, most likely water. The Valley 'flows' North/West, out of the hilly Region of Margaritifer Terra, where the Iani Chaos Depression (approx. 180 Km long and 200 Km wide) is connected to the beginning of Ares Vallis by an about 100 Km wide Transition Zone, centered around 342,5° East Long. and 3° North Lat. It then continues through the ancient Highlands of Xanthe Terra, and then ends in the Delta-like Region of Chryse Planitia. Ares Vallis was the Landing Site (in the AD 1997) of the NASA - Mars Pathfinder Lander (as well as the small Rover, Soujourner), which studied a small area of the Valley that was located near the border with Chryse Planitia.

It has been argued that Uzboi, Ladon, and Ares Valles, although now separated by large craters, once comprised a single Outflow Channel, flowing straight into Chryse Planitia. The source of this alleged (and massive) Outflow Channel has been suggested as an Overflow from the Argyre Crater, formerly a Lake filled to the Brim (---> to the Edge) by several Channels (---> Surius, Dzigai, and Palacopus Valles), all draining down from the South Pole. If this theory were (either just partially) real, the full length of this Drainage System would have been of over 8000 Km: such as the longest known Drainage Path in the Solar System. According to this suggestion, what we see now of the Outflow Channel Ares Vallis would therefore be just a remolding of a pre-existing (larger) structure. A research published in January 2010, suggests that Mars might have had many Lakes, each around 20 Km wide, along parts of the Equator. Although earlier research showed that Mars had a warm and wet early history (that has long since it got cold and dried up), these Lakes should have existed in the Hesperian Epoch: a much earlier period! Using detailed images from NASA - Mars Reconnaissance Orbiter, some researchers speculated that there could have been, during that period, a significant increase of Volcanic Activity, Meteor Strikes and/or even Shifts in Mars' orbit, which all led to the warming of its Atmosphere up enough so to melt most part of the abundant Ice present in the Martian Ground. At the same time, the simultaneous eruption of a few Volcanoes would have caused the release of huge amounts of Greenhouse Gases whose action, in a (Geologically speaking) short time, thickened the Atmosphere of the Red Planet for (again: always relatively speaking) a long period, thus trapping more Sunlight and making Mars warm enough for Liquid Water to resist and flow on its Surface. In this new study (see, if you wish, ScienceDaily of January, 4, 2010) it is reported that many other Channels connecting (possible) Lake Basins near Ares Vallis were discovered. When one of these Lakes filled up, its waters then Overflowed the Banks and carved other Channels which flew into lower areas and formed other Lakes. Given all that, the Floors of these (alleged, of course) Martian Lakes would be another good place where to look for evidence of an either still present (why not?) or a past (and, in this case, probably long gone...) Martian Indigenous Life.

Orbit Number: 45215; Latitude: 2,44° North; Longitude: 343,95° East; Instrument: VIS; Captured: February, 23rd, 2012; Mars Local Solar Time: 06:02 (Early Morning Hours)

This frame has been colorized in Absolute Natural Colors (such as the colors that a human eye would actually perceive if someone were onboard the NASA - Mars Odyssey Orbiter and then looked down towards the Surface of Mars), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team.