» Phobos Moons of Mars Astronomy

Astronomers have at last found definitive evidence that the universe's first dust - the celestial stuff that seeded future generations of stars and planets - was forged in the explosions of massive stars.

The findings, made with NASA's Spitzer Space Telescope, are the most significant clue yet in the longstanding mystery of where the dust in our very young universe came from. Scientists had suspected that exploding stars, or supernovae, were the primary source, but nobody had been able to demonstrate that they can create copious amounts of dust - until now. Spitzer's sensitive infrared detectors have found 10,000 Earth masses worth of dust in the blown-out remains of the well-known supernova remnant Cassiopeia A.

Space dust is everywhere in the cosmos, in our own neck of the universe and all the way back billions of light-years away in our infant universe. Developing stars need dust to cool down enough to collapse and ignite, while planets and living creatures consist of the powdery substance. In our nearby universe, dust is pumped out by dying stars like our sun. But back when the universe was young, sun-like stars hadn't been around long enough to die and leave dust.

That's where supernovae come in. These violent explosions occur when the most massive stars in the universe die. Because massive stars don't live very long, theorists reasoned that the very first exploding massive stars could be the suppliers of the unaccounted-for dust. These first stars, called Population III, are the only stars that formed without any dust.

Phobos Moons of Mars

Filed under: Mars — admin @ 7:22 pm

Phobos Moons of Mars Phobos [FOH-bohs] (fear) is a moon of Mars and was named after an attendant of the Roman war god Mars. Phobos is a dark body that appears to be composed of C-type surface materials. It is similar to the C-type (blackish carbonaceous chondrite) asteroids that exist in the outer asteroid belt. Some scientists speculate that Phobos and Mars’ other moon, Deimos, are captured asteroids. However, other scientists point to evidence that contradicts this theory. Phobos shows striated patterns which are probably cracks caused by the impact event of the largest crater on the moon. Asaph Hall discovered Phobos in 1877.

Phobos Statistics

Characteristic	Measurement
Mass (kg)	1.08e+16
Mass (Earth = 1)	1.8072e-09
Radius (km)	13.5×10.8×9.4
Radius (Earth = 1)	2.1167e-03
Mean density (gm/cm^3)	2.0
Mean distance from Mars (km)	9,380
Rotational period (days)	0.31910
Orbital period (days)	0.31910
Mean orbital velocity (km/sec)	2.14
Orbital eccentricity	0.01
Orbital inclination	1.0Â°
Escape velocity (km/sec)	0.0103
Visual geometric albedo	0.06
Magnitude (Vo)	11.3

Views of Phobos

Phobos

Phobos
This image was taken by the Viking Orbiter spacecraft in 1977. Striated patterns can be seen in this image. These are probably cracks caused by the impact event of the Stickney crater shown below.

Stickney Crater

Stickney Crater One of the most striking features of Phobos, aside from its irregular shape, is its giant crater Stickney. Because Phobos is only 28 by 20 kilometers, the moon must have been nearly shattered from the force of the impact that caused the giant crater. Grooves that extend across the surface from Stickney appear to be surface fractures caused by the impact. Near the crater, the grooves measure about 700 meters across and 90 meters deep. However, most of the grooves have widths and depths in the 100 to 200 meters and 10 to 20 meters ranges, respectively.

Stickney Crater Another View

This image shows a slightly different view of the Stickney crater. A crater within the Stickney crater is visible.

Conformal Projection of Phobos

Conformal Projection of Phobos This shows two different views of Phobos in a Morphographic Conformal Projection. One view shows the leading side and the other the trailing side.

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