Moons of Jupiter and Saturn seeded with life?

A new study by Penn State suggests the possibility of transfer of life from the inner solar system to the moons orbiting Jupiter and Saturn, although very rare, cannot be ruled out.

Life on Earth or Mars could have been brought to the moons of Jupiter or Saturn on rocks blasted off those planets, researchers say.

These findings suggest if scientists ever detect life on those moons, they might have to contemplate the possibility that it came from elsewhere rather than originating there on its own.

The idea that life can spread through space is known as panspermia. One class of panspermia is lithopanspermia—the notion that life might travel on rocks knocked off a world's surface.

If these meteoroids encase hardy enough organisms, they could seed life on another planet or moon.

Although lithopanspermia might seem far fetched, a number of meteorite discoveries suggest it might at least be possible.

For instance, more than 100 meteorites originating from Mars have been discovered on Earth, blasted off the red planet by meteor strikes and eventually crashing here.

Some researchers have even suggested that life on Earth may have originally been seeded by meteors from Mars.

A great deal of research has explored whether the red planet once harbored life and whether life might still exist there today, based on findings that Mars might once have been significantly more hospitable to life than it is now, and that refuges for life could remain hidden under its surface.

Martian meteorite ALH84001. The meteorite is sliced to show its interior. 

Found in the Allan Hills ice field in Antarctica in 1984, the four-billion-year-old rock is one of the oldest in the world. 

The meteorite likely originated just below the surface of Mars. About 16 million years ago, another meteorite struck the area, blasting it off into space before it landed on Earth about 13,000 years ago. 

Credit: NASA

One Martian meteorite, Allan Hills 84001 (ALH84001), was even initially claimed to contain evidence of life.

However, research since has revealed that every item on this meteorite that was potentially suggestive of life could be generated inorganically.

Past computer simulations also have suggested that matter blasted off Earth by cosmic impacts could have escaped the pull of Earth's gravity and landed on the Moon.

Billions of years of Earth dust may have accumulated on the lunar surface—as much as 22 tons (20 metric tons) of Earth material is spread over every 38 square miles (100 sq. km) of the Moon.

If true, the Moon could hold fossils of some of the earliest microbial life on Earth.

The discovery of organisms on Earth that can survive in environments once thought too harsh for life has piqued interest over whether the moons in the outer reaches of the solar system, such as Jupiter's moon Europa or Saturn's moon Titan, could host life.

"There have been previous simulations looking at transfer between Earth and Mars, but we wanted to scale the simulations up in the hopes of seeing transfer to Jupiter and Saturn," said study lead author Rachel Worth, an astrophysicist at Pennsylvania State University.

Worth and her colleagues Steinn Sigurdsson and Christopher House detailed their findings online Dec. 6 in the journal Astrobiology.