Mars: At Opposition
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What is opposition and why does it happen so infrequently between the Earth and Mars? This animation can help to sort that out. With an orbital period of
about 687 days - or roughly 22.5 months - it takes Mars a little less than twice as long to go around the Sun than what we are used to here on Earth. So say
we are at an opposition point - or a point where Mars is perfectly on the opposite side of the Earth from the Sun. Being positioned opposite the Sun
incidentally is the closest point that an outer planet can reach to the Earth. Anyway, the Sun, Earth then Mars are in perfect alignment. Because of the
nature of Mars' orbit this number can vary greatly, let's figure out a hypothetical distance between the Earth and Mars.
Let's say at this particular point in time that Mars is 140 million miles from the Sun (which is roughly its average) and Earth is 95 million miles (which is as far away from the Sun as the Earth gets). Subtract 95 from 140 and you get 45 - so in this example the Earth and Mars would be separated by 45 million miles. A year passes and Earth has made a full orbit - but in the same time span Mars has only made half of an orbit. To keep things simple lets use the same numbers, now to figure the distance you don't subtract those numbers - you add them. So now Earth and Mars are separated by 95 million plus 140 million, or 235 million miles. And if that greatly increased distance wasn't enough to make it tough for us to see Mars, now to see the red planet we'd have to be able to see through the Sun! Which of course we can't. So enjoy opposition when you can, it only happens every other year! |
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| Why do oppositions vary? | Where will Mars be in the sky? | Timeline of Oppositions | How far is Mars at this moment? | |
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