dipper@utastro.UUCP (Debbie Byrd) (07/30/85)
Today we are as far from the planet Mars as we will be all this year. More -- after this. July 30 Our Greatest Distance from Mars Earth circles the sun approximately twice for every single orbit of the planet Mars. We overtake Mars generally every second year -- pass between it and the sun -- so that Mars appears opposite the sun in our sky. Then Mars is closest to us in space -- and brightest in our sky -- a fiery beacon visible from dusk until dawn. At such a time, Mars is said to be at opposition to the sun. The last opposition of Mars was a year ago last May. This year, we haven't been anywhere near Mars in space. We were ahead of it in orbit when the year began -- and when the year ends, when we've come a full circle around the sun, Mars will have moved half of its orbit ahead -- and so will be ahead of us. That's a little hard to visualize without looking at a picture of the orbits of the two worlds. But try to imagine where Mars is this summer -- traveling on one side of the sun -- while we're moving along on the other side -- so that we can't see Mars at all this summer from Earth. The red planet will be hidden in the sun's glare until around early September. Mars was directly behind the sun from Earth on July 17. Today it reaches its greatest distance from us for this year. If you were talking to an astronaut on Mars today, it would take about 45 minutes for a simple question and answer to make the round trip -- using radio waves traveling at the speed of light! Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin