Mars Reconnaissance Orbiter (MRO)
|
|
|
PSP_006648_1300_RED_abrowse-00-PCF-LXTT.jpgSouthern Dunefield (Absolute Natural Colors; credits: Dr Paolo C. Fienga - Lunexit Team)73 visiteSeen here is the Eastern Edge of a Dunefield located in a large, degraded crater in the Southern Hemisphere.
Similar to other Dunes on Mars, these Dunes are dark-toned and contain Gullies. Gullies are features found on Slopes and Dunes in the Mid-Latitudes of both Hemispheres. Both Slope and Dune Gullies were initially suggested to be a result of liquid water from the Surface or Subsurface. Slope and Dune Gullies usually have different morphologies: Dune Gullies are more linear and have Levees bordering their Channels. They typically have no distinguishable, or very small, Alcove and Debris Aprons.
Slope gullies, on the other hand, often have deeply incised Alcoves and Channels that exhibit fluvial characteristics such as Streamlined Islands.
What is highly unusual about this Dunefield is that one of its Gullies has the morphology of a "Slope Gully! (approx. 3 Km across)! This Dune Gully has a very incised Alcove, what appears to be Streamlined Islands on the Channel Floor, and a large, and "feathery" Debris Apron.MareKromium
|
|
PSP_006648_2255_RED_abrowse-PCF-LXTT.jpgScarps in Deuteronilus Mensae (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team:)78 visiteThis image shows Scarps (such as "Steep Slopes") in Deuteronilus Mensae, a Region of distinctive Terrain in the Northern Hemisphere of Mars. Polygonal fractures, possibly formed by thermal cycles in ice-rich ground, are visible throughout the scene.
The high-standing topography at the top of the Scarps have several muted circles: these are Remnant Impact Craters that have degraded throughout time and their degradation process might have been enhanced by the presence of ground ice.
The two Scarps have different morphologies: the lower (East-facing) side has a Debris Apron with a wave-like texture at its base.
This is suggestive of material that has moved down the Scarp and gradually flowed away from it. Such a process would be expected if the material were ice-rich. There is no counterpart of this feature at the base of the upper (such as the West-facing) side.MareKromium
|
|
PSP_006653_1795_RED_abrowse-PCF-LXTT.jpgVolcanic Vent, East of Pavonis Mons (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit) 84 visiteThis image shows an Equatorial Volcanic Vent. A Volcanic Vent is an opening in the Crust of a Planet that emits Lava (such as "molten rock") and Volcanic Gases. The rough texture of the Plains surrounding the Vent is indicative of Lava.
There is a large number of snake-like features emanating from the Vent. The parallel lines that outline the features are "Levees", which mark the edges of Channels that carried molten Lava. As Lava flows, it moves slowest at its edges and bottom because the Lava sticks to the non-flowing rocks; as a consequence of this event, the lava slows down, cools off and, in the end, it hardens.
Levees, on their side, form when the sides of the Lava Flow harden but the center of it keeps moving. As the eruption episode ends, and the Lava drains, the center is left lower than the sides producing these high-standing structures.MareKromium
|
|
PSP_006659_1460_RED_abrowse~0.jpgGullies in Dao Vallis (MULTISPECTRUM; credits: Lunexit)54 visiteGullies on the North-West side of Dao Vallis, a Martian outflow channel, are the focus of this observation. The outflow channels are thought to have been carved by gigantic, ancient floods.
Gullies are largely thought to be the result of water flow, but the origin of the water is much debated.
One theory proposes that melting snowpack, or a mantling (blanketing) unit, forms gullies. Such a mantling unit is visible here between some of the gullies, in the full high-resolution image. Some alcove-shaped features appear to have mantling material in them.
If the mantling unit is indeed related to gully formation, then gullies are potentially forming here.
MareKromium
|
|
PSP_006667_2150_RED_abrowse-00-PCF-LXTT.jpgSmall "Cones", North of Olympus Mons (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit) 81 visiteOlympus Mons is the largest Volcano in the Solar System and is thought to have been active in the relatively recent past (which on Mars means many millions of years ago). While this towering giant gets a lot of the attention, it is surrounded by a vast field of other Volcanic Features. This HiRISE image takes a close look at one set of intriguing landforms: small Cones.
Cones similar to these are found atop the freshest Lava Flows on Mars in Athabasca Valles. In that location, HiRISE found proof that they formed by steam exploding through the Lava Flow. The steam was produced by boiling water (or ice) in the ground underneath the Lava Flow. Could the same thing have happened here?
Unfortunately, HiRISE finds that this area north of Olympus Mons is covered in a thick layer of Dust. While the wonderful resolution of HiRISE reveals details of the Ripples in the Dust, it cannot show us what is underneath the Dust. Therefore we cannot prove that these Cones formed the same was as the Athabasca Valles ones.
They could be small Volcanic Vents, but it is unlikely that so many small eruptions would have taken place so close together.
However, since we cannot show that the ground under the Dust is actually Lava, we cannot rule out non-volcanic processes. Still, the similarity in the shapes and sizes of these Cones to the ones in Athabasca Valles leaves open the possibility that Water and Lava interacted explosively here.MareKromium
|
|
PSP_006672_1420_RED_abrowse~0.jpgFeatures of the Hellas Montes (MULTISPECTRUM; credits: Lunexit)56 visiteThe Hellas Montes are a group of mountains along the western rim of the giant Hellas Basin on Mars.
The Hellas Basin is the largest of the obvious impact craters on the Red Planet. It is very ancient and has been partially filled by sediments. The Hellas Montes are part of the eroded crater rim.
In the central part of this HiRISE image, we can see steep slopes where landslides have exposed a variety of rocks. The jumble of blocks, rather than stacks of layered sediments or lavas, is consistent with impact crater ejecta. On flatter slopes, the ground is covered with a mantling deposit that is generally considered to be ice-rich dust.
In the southern part of the image (Dx), a large circular depression — rimmed by a zone with many large boulders — is (barely) visible. This is an impact crater with a relatively thin mantling deposit on its rim.
MareKromium
|
|
PSP_006673_1600_RED_abrowse.jpgBright Material on the Floor of an Unnamed Crater (natural colors; credits: Lunexit)56 visiteThis image shows part of a crater wall and floor, where the floor is covered by dunes and distinct regions of bright material. The bright material stands higher than the rest of the floor suggesting that it is more resistant to erosion than surrounding materials.
It is possible that more and more bright material will be exposed over time; why the material is bright is unknown.
The material might be evaporites, that form when salt water dries up and leaves behind salt deposits (the evaporites).
Also in this scene is a crater with a ridge running up to its west (left) side. The ridge is lighter and might be evidence that water flowed through it, bleaching the rocks as it went. The water might have cemented the soil, causing it to be more resistant to erosion and high standing as seen today.MareKromium
|
|
PSP_006677_1475_RED_abrowse~0.jpgStreamlined Features near Hale Crater (natural colors; credits: Lunexit)56 visiteThis image contains streamlined features located North-West of Hale Crater, a 120 x 150 Km diameter impact crater that is possibly the youngest of its size on Mars.
A streamlined feature is one that is raised, possessing sharp edges. It is narrower at the downstream end because of the flow that carved it. Any fluid — lava, water, mud, and even flowing ice — can form streamlined features. Many portions of the image are filled with craters, while others are rather smooth.
The streamlined features in this image tend to be smoother, suggesting they are relatively young.
Their origin might be related to the impact that formed the crater.
MareKromium
|
|
PSP_006679_1680_RED_abrowse-PCF-LXTT.jpgLayered Features in Noctis Labyrinthus (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)250 visitenessun commentoMareKromium
|
|
PSP_006681_1580_RED_abrowse~0.jpgFresh Southern Crater (natural colors; credits: Lunexit)87 visiteThis image features a very fresh crater in the Southern Hemisphere. The crater is termed fresh because it is well-preserved with steep walls and obvious small-scale ejecta.
The crater has a set of dark rays extending from it; these rays are ejecta that sprayed out when the crater formed. Boulders ejected during the impact surround the crater.
MareKromium
|
|
PSP_006690_2280_RED_abrowse-02.jpgFeatures of Acidalia Planitia (extra-detail mgnf)53 visiteThis HiRISE extra-detail mgnf (358 x 266 mt or 392 x 291 yards) shows incipient scalloped terrain in the Southern Slopes of the Crater.
Scalloped terrain — depressions with scalloped edges and polygonal fractures — has been interpreted as a sign of surface caving, perhaps due to sublimation (evaporation) of underlying ice.MareKromium
|
|
PSP_006695_1415_RED_abrowse~0.jpgGullies in Sirenum Fossae (MULTISPECTRUM; credits: Lunexit)54 visiteThis image shows parts of Sirenum Fossae that are southwest of Gorgonum Chaos. Some of the troughs (Fossae) have gullies on their walls. Gullies are incised slope features that are thought to have formed by liquid water flowing down the slopes.
It is unknown whether the water came from the subsurface or above the surface. The plains around the troughs have a number of mesas and hills that might have formed from erosion of a once-larger rock unit.
The left side of the image shows some dark linear features which MIGHT BE Dust Devil Tracks.MareKromium
|
|
| 2237 immagini su 187 pagina(e) |
 |
|
|
|
|
130 | |
|
|
|
|
