Kiwis on Martian moon mission

EYE INTO SPACE: Tim Natusch was part of an international effort to study the Martian moon Phobos.
EYE INTO SPACE: Tim Natusch was part of an international effort to study the Martian moon Phobos.

New Zealand scientists have been part of a daring fly-by of the Martian moon Phobos which could finally debunk long-held science fiction theories.

Last night the Mars Express spacecraft shot past the moon at a distance of just 45 kilometres - the closest fly-by yet and one that scientists hope may help solve the riddle of why Phobos weighs less than it should.

"According to observations made during a fly-by two years ago, Phobos is too light for its size," Professor Sergei Gulyaev, director of AUT's Institute for Radio Astronomy and Space Research (IRASR) said.

"A natural moon should be much more massive.

"There are even speculations that this cigar-like object is hollow. That will either be confirmed or rejected soon after this fly-by."

The most popular theories have Phobos and the other Martian moon Deimos, as passing asteroids captured into Mars' orbit by the planet's gravity, or as the result of massive collisions with Mars by other bodies. Large gaps between rocks as the resulting debris clumped together could account for Phobos's lack of density.

The 27-kilometre long Phobos has been science fiction fodder as far back as the 1950s and the apparent lack of density has fuelled speculation by some die hard sci-fi fans it is some kind of hollow alien structure.

The reality is likely to be much less explosive for humanity but still immensely interesting for scientists, said IRASR deputy director Tim Natusch, who has been overseeing the university's involvement with the project.

The 5am kick-off yesterday saw him camping overnight at the Warkworth Observatory.

He has also been calibrating and testing the institute's 12-metre radio telescope dish at the Warkworth Observatory to work in unison with a dozen radio telescopes across Australia over the last couple of weeks.

The clusters of dishes from Western Australia across the continent to Warkworth in New Zealand form a 6000km-long array, which Natusch said allowed scientists to not just pick up communications from the spacecraft, but also to take extremely accurate readings of its position and speed even though it was 200 million kilometres away.

The spacecraft's course and speed was expected to change slightly with the moon's gravitational pull. While only likely to be a few centimetres per second, the change should be enough to be detected in the signals being sent back to Earth, he said.

These changes should allow scientists to work out the mass and structure of Phobos' interior and perhaps lay to rest Mars' little green men for good.