If the microbes reproduced, even at very slow timescales, some microbes may indeed be distant descendants of ancestors that were alive when dinosaurs roamed the Earth. But it is also possible that some have subsisted in stasis, capable of resuming normal life functions once conditions change. Tori Hoehler, a specialist in space science and astrobiology, studies extreme microbial life forms on Earth to understand what life on other planets might look like. Hoehler said, “These guys down in the deep subsurface are metabolizing anywhere from ten thousand to a million times more slowly.”
Other research teams have located ancient microbes in similar deep seabeds and provided them with richer food sources than those typically found in their spare natural habitat. These cells once again metabolized food, and emerged from a sort of suspended animation. This means that the North Pacific Gyre microbes might also revive if more nutrients became available to support them. “It seems that these microbes are sort of sitting there, ready to go,” Hoehler said. “And that’s at least some indication that they’re not in a completely unrevivable state, and maybe they are just going very, very slowly.”
Life on Earth and beyond
Studying these microbes gives scientists like Røy and Hoehler a chance to expand the known boundaries for life on Earth, and understand what life forms might thrive in extreme environments that appear uninhabitable. Yet scientists currently know so little about these conditions, even on Earth. Hoehler said, “A third of the life on our planet lives in a physiological state that we have very little insight into.”
Exploring extreme environments can also clue scientists into where life on other planets might be found. While countless science fiction books and films have created wildly imaginative scenarios of what aliens might look and act like, it is far more likely that alien life will resemble the tiny humble microbes found deep in Earth’s seafloor.
“The kinds of conditions we find deep in the subsurface may be more relevant to thinking about life in these other places,” Hoehler said. For instance, it is believed that water exists deep in Europa or in the subsurface of Mars, in conditions similar to Earth’s subsurface environment. “A first step in understanding that is knowing how life on Earth copes with limitation of energy,” Hoehler said. “And what can that tell us about the prospects for life elsewhere?”
References
Hoehler, T. M., and B. B. Jørgensen. 2013. Microbial life under extreme energy limitation. Nature Reviews 11, doi:10.1038/nrmicro2939.
Røy, H., J. Kallmeyer, et al. 2012. Aerobic microbial respiration in 86-million-year-old deep-sea red clay. Science 336 (6083): 922–925, doi:10.1126/science.1219424.
NASA Ocean Biology DAAC (OB.DAAC). SeaWiFS Level 3 data. 2012. Greenbelt, Maryland, USA.
For more information
NASA Ocean Biology Distributed Active Archive Center (OB.DAAC)
Sea-Viewing Wide Field-of-View Sensor (SeaWiFS)
About the remote sensing data |
Satellite |
GeoEye SeaStar |
Sensor |
Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) |
Data set |
SeaWiFS Level 3 |
Resolution |
9 x 9 kilometer |
Parameters |
Chlorophyll a and photosynthetically active radiation |
DAAC |
NASA Ocean Biology Distributed Active Archive Center (OB.DAAC) |
The photograph in the title graphic is cropped from the original size and shows an abyssal seafloor in the Pacific Ocean. (Courtesy NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011/Flickr)