Researchers have found evidence of bacteria thriving in volcanic rocks more than 4,000 feet below the island of Hawaii, so it's possible for life to survive in conditions that are as inhospitable as Mars.
For the past 10 years Martin Fisk of Oregon State University in Corvallis has been looking for life in all the wrong places, and and he and his colleagues have found it in everything from Arctic glaciers to rocks collected from the sea floor, covered with more than two miles of water.
The latest discovery resulted from microscopic analysis of core samples from a scientific drilling project near the town of Hilo on Hawaii's Big Island. Fisk and other scientists from a wide range of disciplines and several institutions found tiny burrows carved out by microorganisms that somehow were able to find the nutrients they needed to survive within the rock itself, buried three quarters of a mile below the surface.
Life, With Little Requirements
The scientists also found DNA and RNA, the two molecules necessary for life. Both showed little or no degradation, thus demonstrating that these tiny organisms have been active recently, possibly even on the day the sample was taken from the drill hole.
"RNA especially degrades quite quickly," Fisk says. "That tells us that quite recently there was something living within the rock."
It also suggests something else. If life can survive in such a hostile environment as volcanic rock buried beneath the ground, it probably can survive on many other worlds.
"The conditions are suitable on Mars and some of the bigger moons in the solar system to support life," Fisk says. The volcanic rocks of Hawaii have all the elements necessary for life, including carbon, phosphorous and nitrogen. All that's needed is water to complete the package.
Fisk believes that far below the surface of Mars the temperature will be warm enough to melt the ice that many scientists believe is present on the Red Planet, and if there's water, there's probably going to be bacteria.
"It gets into everything," he says.
Fisk is a professor oceanic and atmospheric sciences at Oregon State, and the lead author of a report on the Hawaii project in the December issue of Geochemistry, Geophysics and Geosystems, published by the American Geophysical Union and the Geochemical Society.
The project was funded by NASA, the California Institute of Technology, and Oregon State, using drilling samples from the Hawaii Scientific Drilling Program, which is funded by the National Science Foundation.
The hole is nearly 10,000 feet deep, and Fisk suspects that microbes probably survive even at that depth, but so far only one area has been studied. The researchers examined thin samples of rock from the entire hole, and zeroed in on the 4000 foot depth because it looked the most promising.
At that depth the volcanic rock consists mostly of fractured basalt glass, or hyaloclastites, which are formed when lava flows into the ocean. The rock at that depth is about 300,000 years old, so it has been buried under many subsequent eruptions. As the researchers examined the rocks, they found evidence that they had been altered in a way that would be consistent with "rock that has been eaten by microorganisms," Fisk says.
But the real proof of the pudding came with DNA analysis that revealed the presence of bacteria that is quite different from your run-of-the-mill microbes. In fact, the bacteria found beneath Hawaii is similar to bacteria collected by Fisk and his colleagues from many other areas that appear very inhospitable to life.
One of the researchers, Carol Di Meo-Savoie of the Medical University of South Carolina, has examined rocks collected from the ocean floor, two to three miles below sea level, and her work suggests that the rock-eating microbes are very different from those found in the sea water where the rocks were collected.
"She figured out what was on the exterior of the rock, what was in the sea water, and what was inside the rock, and it was really clear that the bacteria she got out of the rock was different" from the other bacteria, Fisk says.
In fact, it more closely resembles a totally different type of microorganisms called "archaebacteria," Fisk says. Once thought to be ancient bacteria, archaebacteria is now believed to be a distinctly different form of life, joining bacteria and plants and animals in the kingdom of life.
The discovery raises many questions, including the precise diet that these organisms live on. Fisk says it's possible they just eat the rock, gaining the chemicals, like iron, to oxidize and turn into energy. The best way to find out, he says, is to go back to the hole and collect more DNA and immediately dump it into a culture and see if it survives.
If it does, the researchers should be able to figure out its diet by identifying the nutrients that make it grow.
That could be helpful, he says, in the effort to identify the areas of other worlds where we would best look for life.