Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2003 November 12
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Mars Then and Now
Credit & Copyright: Tom Ruen, Eugene Antoniadi, Lowell Hess, Roy A. Gallant, HST, NASA

Explanation: Does Mars have canals? A hot debate topic of the late 1800s, several prominent astronomers including Percival Lowell not only claimed to see an extensive system of long straight canals on Mars, but used them to indicate that intelligent life exists there. The relatively close opposition of 1894 was used to make drawings like the one digitally re-scaled on the above left. The above map was originally prepared by Eugene Antoniadi and redrawn by Lowell Hess for the book Exploring Mars, by Roy A. Gallant. In more modern times, the latest Mars opposition has allowed the Hubble Space Telescope to capture a picture of similar orientation. Comparison of the two images shows that large features were impressively recorded, but that an extensive system of long and straight canals just does not exist. Satellites orbiting Mars have now shown conclusively that the red planet does indeed have surface features similar to canals, but that these are usually smaller, curved, and less extensive than that previously claimed. Real canyon systems like Noctis Labyrinthus are most likely cracks caused by surface stress.

Tomorrow's picture: aurora OK

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