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TOPIC: Phobos and Deimos
Blobrana


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Title: Formation of Phobos and Deimos via a Giant Impact
Author: Robert Citron, Hidenori Genda, Shigeru Ida

Although the two moons of Mars, Phobos and Deimos, have long been thought to be captured asteroids, recent observations of their compositions and orbits suggest that they may have formed from debris generated by one or more giant impacts of bodies with ~ 0.01 x target mass. Recent studies have both analytically estimated debris produced by giant impacts on Mars and numerically examined the evolution of circum-Mars debris disks. We perform a numerical study (Smoothed Particle Hydrodynamics simulation) of debris retention from giant impacts onto Mars, particularly in relation to a Borealis-scale giant impact (E ~ 3 x 10^29 J) capable of producing the Borealis basin. We find that a Borealis-scale impact is capable of producing a disk of mass ~ 5 x 10^20 kg (~ 1 - 4 % of the impactor mass), sufficient debris to form at least one of the martian moons according to recent numerical studies of martian debris disk evolution. While a Borealis-scale impact may generate sufficient debris to form both Phobos and Deimos, further studies of the debris disk evolution are necessary. Our results can serve as inputs for future studies of martian debris disk evolution.

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Blobrana


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The International Astronomical Union (IAU) has approved four names for features on the Martian moon Phobos.

Lagado Planitia for a 4-km-wide plain located at 19°, 231°.
The feature was named in honour of a fictional city in Jonathan Swift's Gulliver's Travels.

Laputa Regio for a 14-km-wide feature located at 0°, 265°.
The feature was named in honour of a fictional flying island in Jonathan Swift's Gulliver's Travels.

Opik for a 2-km-wide crater located at -7°, 297°.
The feature was named in honour of the Estonian astronomer J. Ernst.

Shklovsky for a 2-km-wide feature located at 24°, 248°.
The feature was named in honour of the Soviet astronomer S. Iosif.



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Blobrana


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Phobos and Jupiter in conjunction

004-1-20110610-9463-Phobos-SRCframes_L.jpg
Conjunction: before, during and after

Earlier this month, ESA's Mars Express performed a special manoeuvre to observe an unusual alignment of Jupiter and the martian moon Phobos. The impressive images have now been processed into a movie of this rare event.
At the moment when Mars Express, Phobos, and Jupiter aligned on 1 June 2011, there was a distance of 11 389 km between the spacecraft and Phobos, and a further 529 million km to Jupiter.
The High Resolution Stereo Camera on Mars Express was kept fixed on Jupiter for the conjunction, ensuring that the planet remained static in the frame. The operation returned a total of 104 images over a period of 68 seconds, all of them taken using the camera's super-resolution channel.

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Blobrana


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The southern hemisphere of Phobos, up close

During the last of a series of eight encounters with the martian moon Phobos, the High-Resolution Stereo Camera (HRSC) on ESA's Mars Express spacecraft acquired a detailed view of the martian satellite. The orbiter flew past Phobos at a distance of only 100 kilometres on 9 January 2011 and imaged the southern hemisphere of the irregularly-shaped moon. Researchers at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) planned the image acquisitions, during which the orbiter was moving past Phobos at 2.3 kilometres per second, and processed the resulting data.
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Blobrana


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Mars Express close flybys of martian moon Phobos
image2-492-20110120-8974-HighresImage-02-PhobosFlyby_large,0.jpg
Stereo-1 channel image of Phobos

Mars Express has returned images from the Phobos flyby of 9 January 2011. Mars Express passed Mars' largest moon at a distance of 100km.


Image3-492-20110120-8974-Anaglyh-03-PhobosFlyby_large,0.jpg
3D Image (red-cyan anaglyph)


image4-492-20110120-8974-SRCimages-04-PhobosFlyby_large,0.jpg
SRC-Images


image5-492-20110120-8974-sequence-05-PhobosFlyby_large,0.jpg
Sequence of 5 HRSC-channels


image6-492-20110120-8974-Grunt-landing-site-06-PhobosFlyby,2.jpg
Planned landing site of the Russian Phobos-Grunt mission

Source

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Blobrana


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Mars Express Close Flybys of the Martian Moon Phobos 2011

We received late yesterday the processed images from the High Resolution Stereo Camera (HRSC) science team and they are fabulous! The HRSC team have provided an excellent set of images and captions showing a 3D view of the moon and the proposed landing site of the Phobos-Grunt mission.
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Blobrana


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Mars moon may have formed like our own

The Martian moon Phobos may have been blasted off its mother planet by a violent impact, or built from fragments of a much larger moon that was destroyed long ago, according to observations from Europe's Mars Express spacecraft.
If confirmed, the result would overturn the prevailing theory that Phobos was once a wandering asteroid that got captured by Mars. That theory was based on the fact that visible light reflected off the moon closely matches the spectrum of a common type of carbon-rich asteroid.
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Blobrana


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Scientists say they have uncovered firm evidence that Mars's biggest moon, Phobos, is made from rocks blasted off the Martian surface in a catastrophic event.
The origin of Mars's satellites Phobos and Deimos is a long-standing puzzle.
It has been suggested that both moons could be asteroids that formed in the main asteroid belt and were then "captured" by Mars's gravity.
The latest evidence has been presented at a major conference in Rome.
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Blobrana


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Martian moon Phobos
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Discovery of Martian moon Phobos. (1877)

Phobos was discovered by astronomer Asaph Hall on August 18, 1877, at the United States Naval Observatory in Washington, D.C., at about 09:14 Greenwich Mean Time  (contemporary sources, using the pre-1925 astronomical convention that began the day at noon, give the time of discovery as August 17 16:06 Washington mean time).
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Blobrana


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RE: Phobos and Deimos
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Phobos flyby images

Images from the recent flyby of Phobos, on 7 March 2010, are released today. The images show Mars' rocky moon in exquisite detail, with a resolution of just 4.4 metres per pixel. They show the proposed landing sites for the forthcoming Phobos-Grunt mission.
ESA's Mars Express spacecraft orbits the Red Planet in a highly elliptical, polar orbit that brings it close to Phobos every five months. It is the only spacecraft currently in orbit around Mars whose orbit reaches far enough from the planet to provide a close-up view of Phobos.
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Phobos.jpg
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