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TOPIC: Phobos and Deimos


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Phobos From 5,800 Kilometers
 
Mars' moon Phobos in color
High resolution (20Mb TIF) | Black and white High resolution (7.5Mb TIF)

The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter took two images of the larger of Mars' two moons, Phobos, within 10 minutes of each other on March 23, 2008. This is the first, taken from a distance of about 6,800 kilometres. It is presented in colour by combining data from the camera's blue-green, red, and near-infrared channels.

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RE: Phobos and Deimos
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These two images taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show Mars' two small moons, Phobos and Deimos, as seen from the Mars Reconnaissance Orbiter's low orbit around Mars. Both images were taken while the spacecraft was over Mars' night side, with the spacecraft turned off its normal nadir-viewing geometry to glimpse the moons. The image of Phobos, shown on the left, was taken at 01:19 UTC on October 23, and shows features as small as 400 meters across. The image of Deimos, shown on the right, was taken at 20:16 UTC on June 7, 2007, and shows features as small as 1.3 kilometres across. Both CRISM images were taken in 544 colours covering 0.36-3.92 micrometers, and are displayed at twice the size in the original data for viewing purposes.

phobosNov1
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demosNov1
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Source
Credit: NASA/JPL/JHUAPL

Phobos and Deimos are about 21 and 12 kilometres in diameter and orbit Mars with periods of 7 hours, 39.2 minutes and 1 day, 6 hours, 17.9 minutes respectively. Because Phobos orbits Mars in a shorter time than Mars' 24 hour, 37.4-minute rotational period, to an observer on Mars' surface it would appear to rise in the west and set in the east. From Mars' surface, Phobos appears about one-third the diameter of the Moon from Earth, whereas Deimos appears as a bright star. The moons were discovered in 1877 by the astronomer Asaph Hall, and as satellites of a planet named for the Roman god of war, they were named for Greek mythological figures that personify fear and terror.
The first spacecraft measurements of Phobos and Deimos, from the Mariner 9 and Viking Orbiter spacecraft, showed that both moons have dark surfaces reflecting only 5 to 7% of the sunlight that falls on them. The first reconstruction of the moons' spectrum of reflected sunlight was a difficult compilation from three different instruments, and appeared to show a flat, greyish spectrum resembling carbonaceous chondrite meteorites. Carbonaceous chondrites are primitive carbon-containing materials thought to originate in the outer part of the asteroid belt. This led to a commonly held view among planetary scientists that Mars' moons are primitive asteroids captured into Martian orbit early in the planet's history. More recent measurements have shown that the moons are in fact relatively red in their colour, and resemble even more primitive D-type asteroids in the outer solar system. Those ultra-primitive bodies are also thought to contain carbon as well as water ice, but to have experienced even less geochemical processing than many carbonaceous chondrites.
The version of the CRISM images shown here were constructed by displaying 0.90, 0.70, and 0.50 micrometer wavelengths in the red, green, and blue image planes. This is a broader range of colours than is visible to the human eye, but it accentuates colour differences. Both moons are shown with colours scaled in the same way. Deimos is red-coloured like most of Phobos. However, Phobos' surface contains a second material, greyer-coloured ejecta from a 9-kilometer (5.6-mile) diameter crater. This crater, called Stickney, is located at the upper left limb of Phobos and the greyer-coloured ejecta extends toward the lower right.
These CRISM measurements are the first spectral measurements to resolve the disk of Deimos, and the first of this part of Phobos to cover the full wavelength range needed to assess the presence of iron-, water-, and carbon-containing minerals.
The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.
CRISM's mission: Find the spectral fingerprints of aqueous and hydrothermal deposits and map the geology, composition and stratigraphy of surface features. The instrument will also watch the seasonal variations in Martian dust and ice aerosols, and water content in surface materials -- leading to new understanding of the climate.

Source: Johns Hopkins University

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The First International Workshop on the Exploration of Phobos and Deimos will be held at the NASA Ames Research Centre, Moffett Field, California, on November 58, 2007.

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The First International Workshop on the Exploration of Phobos and Deimos will be held at the NASA Ames Research Centre, Moffett Field, California, on November 58, 2007.

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Two new maps of Phobos showing named features have been added to the Gazetteer of Planetary Nomenclature. One map is a global view in cylindrical projection, and the other shows north and south hemispherical views.

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During Rosetta's recent Mars swingby, the OSIRIS cameras captured a series of images of Mars and of Phobos transiting Mars' disk. The OSIRIS team have produced a cool animated sequence and a 3D view of the Red Planet.
 The animated sequences (one faster, one slower) show the shadow of Phobos transiting Mars' disk on 24 February; the images were captured around 22:08 CET, a few hours prior to Rosetta's successful Mars swingby on 25 February

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'Practice run’ for Mars sampling mission announced
A British team is working on a concept mission to land a spacecraft on Mars’s small moon, Phobos, take samples from its surface and bring them back to Earth.
Scientists from the Open University and British satellite manufacturer Astrium are involved.
The plan is for a mothership to orbit Mars before it releases a smaller probe onto the surface of Phobos, where it will drill or scoop and sample surface material.
Then it will use chemical thrusters to lift off from the surface of the moon and dock onto the mothership, where it will be automatically packaged into a protective sealed container and flown near to Earth. It will be jettisoned from the mothership to Earth in a ‘hard’ landing.

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Mars' moon Phobos could be the target for a technology trial that would seek to return rock samples to Earth.
A UK team is developing a concept mission that aims to land a spacecraft on the potato-shaped object and grab material off its surface.
These small rock fragments would then be despatched to Earth in a capsule.

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Phobos crater names

Phobos map (409kb, PDF)

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