A remarkably hardy bacterium can survive pressures similar to those generated when asteroids strike blast debris outside Mars, a new study has found, suggesting that microbes can withstand interplanetary travel and potentially seed life on other worlds, including Earth.
The findings, published earlier this week in the journal PNAS Nexusmay prompt scientists to reconsider where life can exist across the solar system and may lead to a reassessment of “planetary protection” rules designed to prevent contamination between worlds.
The new findings lend support to a long-debated theory known as lithopanspermiawho suggests it life can spread between planets by connecting to one ride on fragments of rock blasted into space by massive impacts. However, the idea remains unproven, and clear evidence of past or present life on Mars remains elusive (although researchers have made some exciting discoveries lately).
For the study, Ramesh and his colleagues tested the endurance of Deinococcus radioduransan exceptionally resilient bacterium found, among other things, in Chile’s high deserts. With a thick outer shell and a remarkable ability to repair its own DNA, D. radio duration is known to withstand intense radiation, freezing temperatures, extreme dryness and other harsh conditions similar to those found in space. After all, it has been nicknamed “the bacteria Conan”.
To simulate the forces involved in a asteroid effect, the researchers entered samples of D. radio duration between two steel plates. Using a gas-powered gun, they fired a projectile at about 300 mph (480 km/h), subjecting the microbes to pressures between 1 and 3 gigapascals. By comparison, the pressure on the deepest part of the Earth’s oceans – the crescent Mariana Trench in the western Pacific Ocean near Guam – is about 0.1 gigapascal, meaning that even the lowest pressure in the experiment was about 10 times greater.
Almost all of the microbes survived shocks that generated 1.4 gigapascals of pressure, while about 60% remained alive at 2.4 gigapascals. At lower pressures, the cells showed no signs of damage, although researchers observed broken membranes and some internal cell damage at higher pressures, the study reports.
“We are constantly redefining the boundaries of life,” said Madhan Tirumalai, a microbiologist at the University of Houston who was not involved in the new study. New York Times. “This paper is another example.”
As the pressure increased, the researchers also discovered increased activity in genes responsible for repairing DNA and maintaining cell membranes.
“We expected it to be dead on the first push,” Lily Zhao, a mechanical engineer at JHU who led the experiment, said in the statement. “We started shooting it faster and faster. We kept trying to kill it, but it was very hard to kill.”
The experiment was ultimately terminated, the statement said, because the steel structure holding the plates “fell apart before the bacteria did.”
