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An astrophysicist who died mysteriously while spending the winter at the South Pole may have been deliberately poisoned, police say.

Australian Rodney David Marks, 32, died in May, 2000, from methanol poisoning, while working with 49 others at a research base operated by the United States' National Science Foundation (NSF).

He had been employed at the base by the Smithsonian Astrophysical Observatory, working on the "Antarctic Submillimeter Telescope and Remote Observatory" project.

When flights to the South Pole resumed after the winter, Dr Marks' body was flown to Christchurch and New Zealand police launched an inquiry for the coroner into his death that is still continuing.

A reconvened coroner's inquest in Christchurch yesterday heard that police had faced a largely fruitless four-year struggle to get information from the NSF and contractor Raytheon Polar Services, even after approaching the US Department of Justice.

Detective Senior Sergeant Grant Wormald told the hearing that there was still no definitive evidence as to how the killer dose of methanol came to be in Dr Marks' body.

Methanol, a poisonous liquid used as a fuel or solvent, was kept on the base for cleaning lenses and other tasks.

Dr Marks had needle marks on his arms, but no traces of illegal drugs found in his body.

Police had considered the possibility methanol had been introduced to his food or drink by a third party "as a prank or other sinister intention".

"In my view it is most unlikely that Dr Marks ingested the methanol knowingly," Mr Wormald said.

"Police have not ruled out that this was as the direct result of the act of another person, although there is no evidence that this occurred."

Dr Marks had been a binge drinker, using alcohol to mask his Tourette's Syndrome, but there was also no evidence of him drinking methanol recreationally.

"It seems unlikely as there were ample supplies of genuine liquor available at the base."

Suicide was considered the least likely possibility, Mr Wormald said.

"Dr Marks had recently formed a close relationship with a woman at the base, he was active in his work and socially at the base. He had no financial worries and he was striving towards the completion of a significant piece of academic work."

There had been evidence of a "still" at the base used to make alcohol, but nothing to prove it was in use in 2000.

Since 2002, Mr Wormald said police had been trying to obtain a list of all people on the base when Dr Marks died, and ultimately had to find it themselves on the internet.

A questionnaire forwarded only - after long negotiation - to the others at the base only got nine replies.

Police believed a full investigation into the events leading to Dr Marks' death had been carried out by the US organisations involved but had been unable to get access to it.

"It is impossible to say how far that investigation went or to what end."

Mr Marks' father, Paul Marks, yesterday thanked police for the "arduous task of dealing with people that quite obviously don't want to deal with them".

The court heard that Dr Marks had visited the base's physician, Dr Robert Thompson, repeatedly before he died, complaining of being unwell.

A blood analysis machine on the base known as a Ektachem may have been able to help pinpoint what was wrong, but it was not properly calibrated, a process taking up to 10 hours.

A former South Pole base doctor, William Silva, said even if the cause of Dr Marks' illness had been pinpointed, drugs commonly used for treatment were not available on the base.

Dr Silva said he saw Dr Marks as a "brilliant, witty and steady sort of bloke, who drank to excess on occasion".

Christchurch coroner Richard McElrea adjourned the inquest yesterday and will deliver a written finding at a later date.