For How Long / When Is Mars Eclipsed by the Sun from Earth

SinK

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I have a short story in which a Mars base is constantly transmitting Big Brother style footage to satellites in orbit around Mars and from there to satellites in orbit around Earth. At some point during the transmission I there will be a period of dead air as Earth passes behind the sun (from the Martian POV). My question is:

a) How long would that period of dead air last?
b) How often would it occur (my current guess is roughly every two earth years as per the alignment of Sun to Earth to Mars)?
c) Is there some obvious thing that makes this dead-air implausible? (I am assuming there are no other satellites picking up the transmission from other locations? I think relativity means the break would occur along with line of sight -- radio and light waves travelling the same speed. But this is not my background so are there any other quirks I should take into account. Gravitational lensing maybe?)
 

MaeZe

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If you mean, will the Earth block out the Sun on Mars, it will not. Eclipses depend on the size and location of the Sun and the occulting body.

https://en.wikipedia.org/wiki/Extraterrestrial_skies#The_Sun_from_Mars

With a really good telescope you could see the Earth transit the Sun.

I saw Venus transit the Sun a few years ago. It was fantastic and you could see it with the naked eye. But when Mercury transited, I couldn't find it with binoculars.
 
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Roxxsmom

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You may want to check out the free program/app called Stellarium (available for pcs and macs, and probably various devices now too). It allows you to set a date and location and see a simulation of what the night sky looked like (or will look like), including which planets (and the moon) were up when, constellations, even supernovas. It's a great tool for writers of historical fiction or SF, or even contemporary ones who want to know when the moon would be full for their story or something.

To answer your question, it kind of depends. Mars takes 1.8 years to go around the sun, and we have a one year period. It's hard to calculate off the top of one's head when Mars will disappear from the night sky for us (when this happens, it's because it's on the same side of the sky as the sun from our perspective). I don't think it takes long to go "behind" the sun relative to us, and in fact, it would rarely be truly eclipsed by the sun (because we're all at slightly different inclinations, and the angular size of the sun is pretty small anyway), but when Mars is only "up" during the daytime (when it's near the sun in the sky from our perspective), we can't see it, obviously.