Mars attacks!

>> McGill prof and team claim meteorites can transfer Martian life to Earth

by NAOMI BLOCH

EXTERIOR SHOT: OUTER SPACE--OUR SOLAR SYSTEM--28 MILLION YEARS AGO.

An asteroid tears through space heading towards the fourth planet from the sun: Mars. Smashing into the planet, it sends fragments of Mars' surface hurtling upward. As the rock fragment rips through the Martian atmosphere, it becomes a glowing red ball; the outer layers transform into a glistening surface of glass. The meteorite soars in the direction of Earth.

EXT: ANTARCTIC WASTELAND--DAY--ANGLE ON BRILLIANT SUN IN A BLUE SKY--13 MILLION YEARS AGO.

The Martian meteorite crashes through the Earth's atmosphere--a blazing fireball. It plummets to the icy surface of the Antarctic, burrowing deep within the ground.

CLOSE-UP: METEORITE--STILL STEAMING.

Through the glassy outer layer a primitive life form can be seen. It appears to be pulsing. MYSTERIOUS MUSIC indicates that there is something special inside this rock.

CUT TO: REALITY.

The best story material comes from real life, and God knows audiences have been waiting aeons for a good sci-fi flick. Lucky for us, scientists are providing ample fodder.

Since it was discovered in 1987, scientists have turned to the potato-sized Martian rock found in Antarctica, thrilled that the meteorite comes from a time when Mars may have been a flourishing, life-sustaining planet. Recently, a team of researchers published a paper in Science suggesting that this rock, known as ALH84001, was capable of transferring life from Mars to Earth.

"Most effort in the past to explain the origins of life on Earth was in establishing the inorganic theory," says team member Hojatollah Vali, a McGill University professor. In the early '50s, a scientist named Stanley Miller made a Frankenstein-like effort to create the basic components of life by artificially recreating Earth's early environment. "He mixed the primitive atmosphere of Earth in a laboratory experiment and could create amino acid. Since then, there are many people working in this area to understand if they can form a basic molecule in a test tube." But creating amino acids and figuring out how this leads to the formation of RNA and DNA, the genetic material necessary for life to evolve, is another story.

Seeds everywhere

The notion that bacteria or other basic life forms on Earth originated in space has been around since the age of Greek philosophers. It's called panspermia, meaning "seeds everywhere," but only recently has it started to gain acceptance as something more than speculative fiction.

"When a meteorite passes through the atmosphere, the whole surface of the rock melts," explains Vali. "It reaches a temperature of up to 1,200 C. The idea was that this extreme temperature must kill everything in the rock, and it wouldn't be possible to transfer life to Earth."

But Vali and the rest of his team believe that while the outer two-millimetre shell of the Martian rock did indeed melt, the interior core could not have been heated above 40 C--a temperature too low to sterilize most bacterial life forms. Though they do not believe that this particular meteorite contained any living organisms, their study indicates that any of the millions of Martian rocks that have landed on Earth may have.

Martian magnets

Mars does not have a magnetic field today (a North and South Pole like we have on Earth), but when the meteorite was formed 4.5-billion years ago, Mars did. When rocks form, minerals in the rock carry the magnetic signature of the planet at that time. "Each magnetic mineral has a certain temperature above which it loses magnetic properties, which we call the blocking temperature," explains Vali. "There are certain minerals that have a very low blocking temperature. And one of them is in this rock."

The outer layer of the meteorite melted as it passed through our atmosphere and became remagnetized by the Earth's magnetic field. But the rock's interior showed different patterns of magnetization. "We heated this rock slowly from room temperature to 40 C, and when we reached 40 some of this magnetic signature became weaker." If the rock's interior had been heated upon entry, the mineral with a blocking temperature of 40 degrees should have taken on the Earth's magnetic direction at the time it was heated. "Since that is not the case, we conclude that the rock wasn't heated above this temperature."

"The first bacteria we know on Earth, in the form of a fossil, is 3.5-3.8 billion years old," says Vali. "But we don't really understand what existed before that point. Bacteria can't just come like that. It has to come from somewhere. That's what we are trying to understand."

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