THE news that NASA scientists have discovered flowing water on Mars has excited interest in the Red Planet, but did not come as too much of a surprise to local astronomers.

The president of the Coffs Harbour Astronomical Society, Win Howard, said even using telescopes much less powerful than the tools available to NASA, local astronomers had long thought there was water on Mars.

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"Mars, like the earth, has polar ice caps, although they are probably largely frozen carbon dioxide," Mr Howard said.

"Also like the earth, Mars has a tilted axis, which means it has seasons. In the warmer seasons we can see a darker patch which looks like dampness at the edge of the ice cap.

"This is exactly what you'd expect to see as the ice caps melted and there was run-off from them."

Mr Howard said of all the other planets in the solar system, Mars was the only one where humans could visit.

"Mercury is too hot, Venus is just too inhospitable, but Mars would be bearable," he said.

"In the middle of summer at the Martian equator, the temperature reaches a balmy 20°C, but that's about where the pleasure would stop. The atmosphere is about 1% of earth's."