| Risultati della ricerca nelle immagini - "Antoniadi" |
Antoniadi-UVVis.jpg160 - Antoniadi Crater55 visitenessun commento
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ESP_012435_2015_RED_abrowse.jpgBranched Features on the Floor of Antoniadi Crater (Natural Colors; credits: Lunar Explorer Italia)55 visiteThe dark branched features in the floor of Antoniadi Crater look like giant ferns, or fern casts. However, these ferns would be several miles in size and are composed of rough rocky materials.
A more likely hypothesis is that this represents a channel network that now stands in inverted relief. The channels may have been lined or filled by indurated materials, making the channel fill more resistant to erosion by the wind than surrounding materials. After probably billions of years of wind erosion the resistant channels are now relatively high-standing. The material between the branched ridges has a fracture pattern and color similar to deposits elsewhere on Mars that are known to be rich in hydrated minerals such as clays.
The inverted channels have short, stubby branches characteristic of formation by groundwater sapping. Spring water seeps into the channels and undercuts overlying layers which collapse, so the channels grow headward. These images tell the story of an ancient wet environment on Mars, where life could have been possible. Ancient Martian life was most likely to consist of microorganisms rather than giant tree ferns.
MareKromium
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ESP_012725_2015_RED_abrowse.jpgBranched Features on the Floor of Antoniadi Crater (Natural Colors; credits: Lunar Explorer Italia)55 visitenessun commentoMareKromium
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PSP_007095_2020_RED_abrowse~0.jpgInverted Dendritic Stream Channels in Antoniadi Crater (MULTISPECTRUM; credits: Lunexit)55 visiteThis observation is centered within Antoniadi Crater. This crater, even prior to the MRO mission, was identified as a likely ancient lake (now dry) that was supplied by both surface water and ground water.
The image provides further tantalizing evidence of a water-rich past. Most of the flat parts of the image have a polygonal texture, which commonly forms when mud dries. In the center of the image are branched (“dendritic”) features that connect Southward to a larger trunk-shaped landform; the branches resemble stream channels on Earth. Unlike active channels with water, these features are “inverted”, or elevated above the surrounding terrain.
Again, in analogy with such features seen on our Planet, these probably formed when materials deposited by the streams, such as coarse gravel, or chemical cementation after removal of the water, caused the channel bottoms to become resistant. Over time, natural erosion from wind and other processes left the inverted channels elevated above the surrounding terrain.
The branched features are probably remnants of small tributary streams that fed the larger trunk-shaped stream. It appears that the inverted streams lie on top of, and are therefore younger, than the polygons. This area may have first had a lake that later dried to form the polygons, followed by episodes of stream flow and erosion.MareKromium
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Psp_009442_2030_red.jpgAntoniadi Crater (possible True Colors; credits: Lunar Explorer Italia)56 visiteMars Local Time: 15:22 (early afternoon)
Coord. (centered): 22,9° North Lat. and 53,5° East Long.
Spacecraft altitude: 282,0 Km (such as about 176,2 miles)
Original image scale range: 56,4 cm/pixel (with 1 x 1 binning) so objects ~1,69 mt across are resolved
Map projected scale: 50 cm/pixel
Map projection: EQUIRECTANGULAR
Emission Angle: 0,3°
Phase Angle: 46,1°
Solar Incidence Angle: 46° (meaning that the Sun is about 44° above the Local Horizon)
Solar Longitude: 106,5° (Northern Summer)
Credits: NASA/JPL/University of Arizona
Additional process. and coloring: Lunar Explorer ItaliaMareKromium
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m10_aom_2_10.jpgThe "Antoniadi" Ridge of Mercury (HR)55 visiteAntoniadi Ridge, over 450 Km long, runs along the right side of this image. The ridge transects a large crater (80-Km in diameter) and in turn appears to be interrupted by an irregular rimless depression on the floor of the crater. This ridge also crosses smooth plains to the north and intercrater plains to the south of the large crater.
This image (FDS 27325) was acquired during the spacecraft's first encounter with Mercury.
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