Phobos passes Jupiter... as seen from Mars!

Bad Astronomy
The entire universe in blog form
June 17 2011 12:40 PM

Phobos passes Jupiter... as seen from Mars!

Mars Express is a European Space Agency probe that's been orbiting the Red Planet since 2003, returning vast amount of data. Lately it's been taking some amazing images and video of the tiny Martian moon Phobos, and the ESA just released this amazing footage of the lumpy potato moon passing by Jupiter as seen from the orbiting craft:

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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How cool is that? Engineers saw this viewing opportunity and actually changed the orbit of Mars Express to be able to see it. Phobos passed a mere 11,400 km (6800 miles) away when these shots were taken, but Jupiter was 530 million km (320 million miles) in the background. That's why a moon only 27 km (16 miles) across can appear to dwarf a planet 140,000 km (86,000 miles) across! In the diagram here, the relative positions of all four players is shown; click to enbarsoomenate.

The animation consists of 104 frames taken over a period of just over one minute. It's useful, too. By knowing the position of the spacecraft and Jupiter, the orbit of Phobos itself can be better determined. Phobos is weird: it orbits so close to Mars that tidal drag is actually lowering its orbit. In roughly 10 million years the moon's orbit will have dropped so much it will impact the planet!

One other thing: my love for red/green 3D anaglyphs is on record. So I was delighted to see the ESA also put this terrific one up:

I know, it's just a gee-whiz thing, but I can be a kid too sometimes. That's simply cool!

Credits: ESA/DLR/FU (G. Neukum) & USA Today



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