A European probe is tonight skimming past a moon that was once thought to be an alien spacecraft. Mars Express will swoop less than 42 miles over Phobos, one of two natural satellites orbiting the red planet.
The flypast – the closest ever – will allow scientists to measure deep inside the 17 mile wide, potato-shaped moon to see just what it is made of.
Phobos, thought to be an asteroid captured by Mars’s gravity, has an unusual low orbit that is taking it spiralling slowly towards an impact.
According to the European Space Agency’s Phobos blog, that led to US President Dwight Eisenhower being briefed in 1960 that it could be a space station launched by an advanced Martian civilisation. (NB: The ESA blog entry has now been removed).
Scientists at the time thought that drag from the atmosphere was causing Phobos to sink in its orbit by around two inches a year – and for that to happen, some said it had to be hollow like an Easter egg.
A Russian suggestion was apparently that the moon could not therefore be a natural object and might be an ancient abandoned spacecraft. Fred Singer, a special advisor on space to the White House, was said by ESA to have passed this information on to the President. However, noted atmospheric physicist Professor Singer, who is now 85, tells us he did no such thing and in fact, he was instrumental, with Ernst Opik (see below), in coming up with the correct explanation for Phobos’s descent – a deceleration caused by Mars’s tidal pull.
There will be no photos from the close encounter because Mars Express will be on Phobos’s night side. The image here was taken on a previous flyby.
Mars scientists will probe Phobos’s real interior by listening to its gravitational effect on a radio signal from their spacecraft during the flyby. Mars also has a smaller nine mile wide moon called Deimos.
LibDem MP Lembit Opik’s grandfather Ernst Opik first noted (with Singer) the correct reason for Phobos’s strange orbit in 1964. The moon must have an irregular shape and the pull of Mars’s gravity created a tidal force that robbed it of energy.
As Star Wars fans might say: “That’s no space station … it’s a moon!”
Note added on March 9: I am very happy to edit this story to make clear the correct nature of Professor Singer’s involvement in solving this remarkable riddle from the history of Mars exploration.
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