Life on planets such as Earth or Mars could have been seeded by electrically charged microbes from space, suggests a new study.
Since the discovery of meteorites from Mars on Earth in the 1990s, people have speculated that living microbes could have travelled back and forth between the two planets, perhaps allowing one planet to seed the other with life.
The problem with this idea is that such a trip could only happen after a huge asteroid collided with one of the planets, with an impact large enough to blast rocks off the planet's surface, and such strikes are extremely rare: just a handful are thought to have occurred since the solar system formed.
However, a new study suggests there may be a much gentler and steadier way for microbial life to leave a planet and travel to other worlds - and even from one solar system to another, something even the biggest impacts could not do.
The startling conclusion grew out of work by Tom Dehel, an electrical engineer at the US Federal Aviation Administration, who was investigating how electromagnetic fields in the Earth's atmosphere can affect GPS satellites and disrupt their use for aircraft navigation. He presented his findings at the biennial meeting of the international Committee on Space Research (COSPAR), in Beijing, China, this week.
Dehel calculated the effect of electric fields at various levels in the atmosphere on a bacterium that was carrying an electric charge. He showed that such bacteria could easily be ejected from the Earth's gravitational field by the same kind of electromagnetic fields that generate auroras. And these fields occur every day, unlike the extraordinarily large surface impacts needed to eject interplanetary meteorites.
The measurements of field strength vary greatly at different levels of the atmosphere - the strongest ones are near the surface, generated by thunderstorms. There are large gaps where the fields have not been measured directly, but assuming the fields extend through the whole air column, there could be an ongoing, sustained process of lofting bacteria high into the atmosphere.
Since the upward forces of the magnetic field would balance the force of gravity for tiny organisms, they could float in the upper atmosphere for years and reproduce there, giving them a chance to evolve capabilities to endure the hardships of that environment, including coping with strong UV and a near-vacuum. Such organisms would thus be well equipped to endure the rigours of a journey through space, Dehel told New Scientist.
The idea that microbes could be electrically levitated into the upper atmosphere was first suggested in 1908 by chemist Svante Arrhenius, but until recently there had been no direct measurements of the strength of electric fields high in the atmosphere to show whether the mechanism would work to propel microbes away from the planet.
Other researchers have already demonstrated that some bacterial spores can survive in conditions thought to exist in interplanetary space, and then be revived. So the possibility of interplanetary spread of life is plausible and deserves further investigation, Dehel believes.
Charged microbes could also be propelled outwards from a planet at high speed by “magnetospheric plasmoids” - independent structures of plasma and magnetic fields that can be swept away from the Earth’s magnetosphere. Hitching rides on these structures could accelerate microbes to speeds capable of taking them out of the solar system and on to the planets of other stars.
And because of the potential for a steady outflow of the particles pushed by the electric fields, a single life-bearing world might seed an entire galaxy with life, claims Dehel.
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