I am writing a story on Mars. Can anyone tell me how big and bright its micromoons Deimos and Phobos appear as seen from the surface? How fast do they move across the Martian sky? Are they usually both visible at the same time?
Here’s a web page that answers most of your questions:
Gees, Podkayne, you probably could have sent him personal photos.
Not mentioned in Podkayne’s link is that since Deimos orbits more slowly than Mars, its apparent motion is retrograde: it moves west to east across the sky, instead of east to west like Phobos and the Sun (I may have that backwards, but you get the idea).
Also, Phobos’s orbit is so tight that at very high Martian latitudes, the moon is below the horizon!
For this and similar topics about our solar system, I direct the OP to the site Nine Planets. It’s a great resource.
You rang?
Um, big error on that page. They have the size of both moons way off, I think they used kilometers when they meant meters.
Thanks to all for the responses.
Which page has the error - “harmsy” or “Nine Planets”?
Perhaps he’s talking about the *orbital[/] radii on the harmsy page? Or maybe the pages are changing as we speak. I couldn’t get that Nine Planets site to come up, but there are other mirrored sites and they seem to have the right radii.
Check out these essays by Asimov:
(http://www.clark.net/pub/edseiler/WWW/essay_guide.html)
Kaleidoscope in the Sky
Subject: satellites of Mars
First Published In: Aug-67, The Magazine of Fantasy and Science Fiction
Collection(s): 1968 Science, Numbers, and I
The Sons of Mars Revisited
Subject: satellites of Mars
First Published In: Nov-77, The Magazine of Fantasy and Science Fiction
Collection(s): 1979 The Road to Infinity
Dark and Bright
Subject: satellites of Mars
First Published In: Dec-77, The Magazine of Fantasy and Science Fiction
Collection(s): 1979 The Road to Infinity
The Real Finds Waiting
Subject: satellites of Mars
First Published In: Jan-78, The Magazine of Fantasy and Science Fiction
Collection(s): 1979 The Road to Infinity
You’ll find lots of good info, including how the moons look as seen from the surface of Mars.
One of those sites said that Phobos would appear one third the size of our full moon. With its tight orbit, all those craters, and its irregular shape, it must look pretty freaky against that pink Martian sky as seen from the surface. Have any of our landers ever snapped a photo of the Martian moons from the surface? Maybe during one of those frequent eclipses?
Sputnik:
Yes, the Pathfinder/Sojourner mission snapped a few low-resolution pics of each moon. I think they were all at night, though.
I don’t have a link handy but if you search on Pathfinder or Sojourner it should be easy enough to find.