Mars Images — MarsWatch 2005

Images taken by James F. Bell and the Hubble Heritage Team

Monday, 07th of November 2005

Attached is an RGB composite of our HST WFPC2 images of Mars from November 7;
a JPEG and an annotated JPEG that provides some more information on features 
of interest.

The images that went into the composite were obtained through the F410M, F502N, 
and F631N filters from 04:27 to 04:33 UT on 2005-11-07, within about four hours 
of the lowest phase (difference between Sun-Mars angle and Earth-Mars angle) 
that Mars has had during the lifetime of HST (around 0.31 degrees--effectively 
zero because that's about the same angle that the Sun subtends from Mars).  
This is the most "Full Mars" anyone can ever see from Earth, and we're still 
trying to figure out if we saw the so-called "opposition effect" brightening in 
these images.  It's hard to tell because HST only observed Mars twice this 
opposition, on Oct. 28 (phase angle around 9 degrees), and Nov. 7, and opposite 
sides of the planet were viewed. We have to compare these images to ones from 
the past decade of HST Mars images to figure it out...  In our spare time...

The "divot" taken out of the right side of the planet near the equator is real, 
and might be related to the high volcano Arsia Mons being almost exactly on the 
limb and for whatever reason (weather, probably) having fewer clouds than the 
surrounding plains at this particular time. Interesting geometric/meteorologic 
effect.  The smallest features resolvable in the image (small craters and wind 
streaks) are about 35 km across.

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