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Planetary News: Mars (2007)

Not This August, or Any August! Mars Will Not Be as Big as the Full Moon

 

By Bruce Betts
August 14, 2007
Mars during the 2003 opposition
Click to enlarge >
Mars during the 2003 opposition
This photo was captured by the Hubble Space Telescope during Mars' closest approach to Earth in over 60,000 years, on August 27, 2003. The view shows the triangular, dark shape called Syrtis Major to the right of center, and the equatorial dark stripe called Sinus Meridiani to the left of center. The giant, ancient Hellas Basin is the circular feature at lower right. Source Credit: NASA, J. Bell (Cornell University), and M. Wolff (Space Science Institute)

In what seems like an August tradition, e-mails and web postings circulating around the Internet say that Mars will be brighter than it has been in thousands of years, and that it will look as big as the full Moon. Neither of these statements is true, although Mars will be very bright and easy to observe during the fall and winter of this year. The origin of the rumor is presumably linked to the fact that Mars was indeed closer to Earth than it had been in tens of thousands of years -- in August 2003. But even during that close approach, Mars appeared as a point of light in the sky.

While I do want to fight misinformation -- I still want to remind you to look up! We shouldn't need an excuse like "closest approach for 60,000 years" to look up and see the planets. Right now, Mars rises in the middle of the night in the east, but it will become visible in the evening sky and will get much brighter as we approach opposition at the end of the year.  And, Jupiter is the brightest star-like object in the evening sky.

Here is more information about Mars viewing in 2007:

- In 2007, Mars will be closest to Earth on December 18.

- Mars never appears large enough to be more than a point of light to the naked eye, and certainly not coming anywhere near the apparent size of the Moon in our sky!

- In 2007, Mars will be significantly farther than it was in 2003, but closer than it will be at its next opposition in 2010. In December 2007, it will still be nice to see as it will be about as bright as the brightest star in the sky, but not nearly as bright as Jupiter or Venus.

- Because of the combination of Earth's and Mars' orbital periods, Mars and Earth grow closer every 26 months. Even then, they are still many tens of millions of kilometers away from each other.

- Martian close approaches vary a lot in brightness because Mars' orbit is much more elliptical (less circular) than Earth's. So, sometimes we are "close" to it when it is in the part of its orbit that is nearest the Sun, and sometimes when it is farthest in its orbit from the Sun.

- Mars was indeed closer to Earth in the 2003 close approach than it had been in tens of thousands of years, but not by much compared with approaches that happened tens of years ago.

- Mars will be about 16 arcseconds across during the 2007 close approach, which is about 9 arcseconds smaller than in 2003. But, the disk will be clear in almost any small telescope. A nice amateur telescope should allow you to see at least a polar cap and some light and dark markings on the surface.

- The actual date of Mars opposition -- the moment when Earth and Mars are at precisely the same longitude with respect to the Sun -- is December 24, 2007. But because of the non-circular shapes of Mars' and Earth's orbits, Mars gets closest to Earth about a week earlier, on December 18.

- Distances of Mars from Earth during each of the recent oppositions were approximately as follows (in millions of kilometers): 2003: 56;  2005: 69; 2007: 88; 2010: 99.  Take heart, in 2018, it will be only 58 million kilometers away.

As December approaches, be sure to check out the real Mars opposition. You can listen to the "What's Up?" segment of our weekly radio show, Planetary Radio, during which we cover easy things to look for in the night sky, so you can keep track of all the bright planets, whether or not they look as big as the full Moon.