Explanation:
Astronomical spring
came to
planet Earth's northern hemisphere
this week (and autumn to the south) with the
equinox
on March 20th.
But on Mars,
northern spring began on January 22nd.
Still in northern springtime,
the Red Planet currently has a similar appearance
to
this composite
of images from previous years taken
by the long-lasting
Mars Global Surveyor
spacecraft.
The sprawling dark region near picture center is
Syrtis Major,
with the whitish
Hellas impact basin just below, in the southern
hemisphere.
The four seasons on Earth each last about 90 earth days,
while Mars' larger and more eccentric elliptical
orbit
results in
seasons that
are longer and vary more widely in length - from about
140 to 190 martian sols.
