It helps to put things in perspective for me ... I hadn't seen the site but the recent news from Mars has me interested in the mysteries of life .... I feel that all that separates me from the inner/outer universe is a lot of skin and two eyes .... which is more than Lady Cassandra can say ....
I expect I'll spend some time browsing that site when I have fresher eyes (it's late-ish here) ...
It's been running since around '96 and has a pretty picture each day. The RSS feed is a nifty full image not a digest too.
If you want to go really nerdy like me you can dig out the raw images from the Mars landers, stitch them, print them and put them up on your walls. But maybe thats going a little far...