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Credit & Copyright: Cenk E. Tezel,
Tunç Tezel
(TWAN)
Explanation:
This composite of images spaced some 5 to 7 days apart
from late October 2011 (top right) through early July 2012
(bottom left), traces the
retrograde motion of ruddy-colored Mars through
planet Earth's night sky.
To connect the dots in Mars' retrograde loop,
just slide your cursor over the picture
(and check out
this
animation).
But Mars didn't actually reverse the direction of its orbit.
Instead, the apparent backwards motion with
respect to the background stars is a
reflection of the motion of the Earth itself.
Retrograde motion
can be
seen each time Earth overtakes
and laps planets orbiting farther from the Sun, the
Earth moving more rapidly through its own relatively close-in orbit.
On March 4th, 2012 Mars was opposite the Sun in
Earth's sky, near its closest and brightest at the center of this picture.
Just arrived
on the
surface of the Red Planet, the
Curiosity rover was launched on November 26, when Mars was
near the crossover point of its retrograde loop.
Of course, Mars can now be spotted
close to Saturn and bright star Spica, near
the western
horizon after sunset.
New Curiosity Images:
Including
360 degree panorama and
rover self portrait
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NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day