A gargantuan earth drawing in South Australia continues to be one of the world’s biggest unsolved mysteries 20 years after it was first discovered.

The Marree Man – a towering 4.6 kilometres-long figure of an ancient hunter etched into the desert – was first spotted in June 1998 by outback pilot Trevor Wright.

The ground drawing – or geoglyph – can only be seen from the sky.

The Marree Man in South Australia was discovered by a pilot in 1998.

Numerous theories about its origins have since been put forward, including suggestions it was a stunt pulled by local scenic flight operators to drum up business.

Over the past two decades, there's been no shortage of people willing to crack the desert enigma, 700kms north of Adelaide, south-east of Lake Eyre.

'HOW HAS IT BEEN KEPT A SECRET'

One of the keenest to get to the bottom of the Marree Man is entrepreneur Dick Smith who earlier this year offered a $5000 reward for information about its origins.

But he told nine.com.au his expert panel investigating the desert mystery remains in the dark despite poring over a mountain of charts, satellite images and other evidence.

Entrepreneur Dick Smith has offered a reward of $5000 to solve the Marree Man mystery. (Dick Smith)

"We're not one step closer," he said.

However, Mr Smith believes it could only have been created with the aid of GPS technology – which was in its infancy and not available to the public back in 1998.

"There were no mistakes, it was very professionally done. And it would have required a good deal of money back then."

"I can't see how it was done by one person, you'd have to have three or four to do it, and it would take weeks to put in.

(Nine)

"In that case, how has it been kept secret for 20 years?"

AMERICAN ORIGINS?

One of the most popular theories is that the Marree Man has American roots.

Immediately after its discovery, press releases were anonymously faxed to the Marree Hotel in the tiny township 60kms away and to an Adelaide newspaper, describing "the world's largest work of art." 

Part of the plaque found near the Marree Man in 1998. (twitter)

However, the writing used American spelling and language, including the use of miles rather than kilometres.

There was further evidence pointing to an American creator including a buried plaque bearing the image of the US flag and the Olympic rings.

But Mr Smith dismisses these as red herrings and believes the Marree Man's origins lay much closer to home.

The 'Marree Man' is visible from space (Supplied)

He thinks it was the work of the "Adelaide establishment" – figures within the SA government and business community - in an attempt to raise the state's global profile.

"I reckon some blokes were standing around a government department or university who had access to GPS software said: 'Let's go out and test this stuff.'"

DESERT WHODUNNIT

The Marree Man etching totals 28 kilometres and represents the image of a mythical giant man holding a hunting stick.

Named after the nearby township of Marree, no one has claimed responsibility for it.

The Nazca Lines in Peru includes the etching of this bird-like creature in the desert. (Getty)

Theories about is origins include it being a parting gift from the US military that trained in the nearby Woomera Prohibited Area alongside Australian forces. Other suggestions have included that it was the work of Aboriginal artists.

Originally dug to a depth of about 35cms, the artwork began to fade but a restoration project in 2016 by local residents approved by the land's traditional owners saved it.

The Marree Man is considered the world's second largest geoglyph behind the 1000-year-old Nazca Lines in Peru.

'MYSTERY AND INTRIGUE'

Few no more about the bizarre artwork than Phil Turner, owner of the Marree Hotel.

"After 20 years, it is still an extraordinary mystery," he said.

"I still get carried away by the myth, mystery and intrigue, the fact they can't find the people who did it," he told nine.com.au.

The Marree Man is located close to the Woomera defence training facility frequented by the US military. (Getty)

"I believe a lot of people were involved in its creation, and a lot of them are still keeping quite about it."

He was one of the driving forces behind the restoration of the Marree Man two years ago and has heard all the theories about its origins.

They include the one that South Australian artist Bardius Goldberg created it.

Goldberg was reported by the Adelaide Advertiser to have told friends he'd been paid $10,000 to create an artwork visible from space. But he died in 2002 and with him perhaps the possibility of finding the accuracy of that theory.

Publican Phil Turner at the Marree Man site. (Supplied)

But Mr Turner has his own view on its origins that revolves around ownership of the land The Marree Man is etched upon.

Since 2012, the land has been held under native title by the Arabana Aboriginal Corporation.

"The hair and the headband on the Marree Man, that was not an Arabana practice. That was more associated with someone from the Musgrave Ranges," he said.

"So why would there be an image of someone from the Musgrave Ranges in Arabana territory?

Mr Turner believes the artwork was created to make the statement: 'This is my land and I'm going to claim it.'

The tiny township of Marree in northern SA is 60 kilometres from the giant desert figure. (Facebook)

He believes that accurately creating the huge figure before public access to GPS technology required expert knowledge and skill as well as rare equipment back in 1998.

He points to a giant mining business or even the Department of Defence being behind it.

But whatever its origins, the Maree Man should be celebrated as a symbol of native land rights, Mr Turner says.

"It's one of Australia's greatest whodunit stories. And I think whoever was behind it needed an intimate knowledge of Aboriginal culture and tradition.

"But it is still a symbol of Aboriginal struggle."

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