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We may all be Martians, according to scientists who recently discovered more evidence that life on Earth may have started on Mars.

"In addition, recent studies show that these conditions, suitable for the origin of life, may still exist on Mars," Professor Steven Benner, from The Westheimer Institute for Science and Technology in the USA, said in at the annual Goldschmidt conference.

Benner explained that an oxidized mineral form of molybdenum, an element that may have been crucial to the origin of life, could only have been available on the surface of Mars and not on Earth.

"It's only when molybdenum becomes highly oxidized that it is able to influence how early life formed," Benner said.

"This form of molybdenum couldn't have been available on Earth at the time life first began, because three billion years ago the surface of the Earth had very little oxygen, but Mars did. It's yet another piece of evidence which makes it more likely life came to Earth on a Martian meteorite, rather than starting on this planet," he explained.

At the conference, researchers presented two paradoxes that have made it difficult for scientists to understand how life could have started on Earth.

The first paradox is called the "tar paradox", which states that all living things are made of organic matter.  However, adding energy like hear or light to organic molecules and leaving them to themselves will not create life.  Instead, the organic materials will just turn into something like tar, oil or asphalt.

"Certain elements seem able to control the propensity of organic materials to turn into tar, particularly boron and molybdenum, so we believe that minerals containing both were fundamental to life first starting," Benner explained. "Analysis of a Martian meteorite recently showed that there was boron on Mars; we now believe that the oxidized form of molybdenum was there too."

The second paradox is that it would be hard for life to start on early Earth because the planet was likely to have been totally covered in water. Researchers explained this would have prevented life from forming because water is water is corrosive to RNA, which scientists believe was the first genetic molecule to appear. What's more, the watery planet would have prevented sufficient concentrations of boron from forming.  Currently, boron is only found in very dry places like Death Valley.

"The evidence seems to be building that we are actually all Martians; that life started on Mars and came to Earth on a rock," says Professor Benner. "It's lucky that we ended up here nevertheless, as certainly Earth has been the better of the two planets for sustaining life. If our hypothetical Martian ancestors had remained on Mars, there might not have been a story to tell."