Microbes from within this lava tube on Newberry Crater in Oregon were cultured under conditions like those on Mars. Photo: Amy Smith, Oregon State University |
A
team of scientists from Oregon has collected microbes from ice within a
lava tube in the Cascade Mountains and found that they thrive in cold,
Mars-like conditions.
The
microbes tolerate temperatures near freezing and low levels of oxygen,
and they can grow in the absence of organic food. Under these conditions
their metabolism is driven by the oxidation of iron from olivine, a
common volcanic mineral found in the rocks of the lava tube. These
factors make the microbes capable of living in the subsurface of Mars
and other planetary bodies, the scientists say.
The findings, supported by a grant from the National Aeronautics and Space Administration (NASA), are detailed in the journal Astrobiology.
“This
microbe is from one of the most common genera of bacteria on Earth,”
said Amy Smith, a doctoral student at Oregon State University and one of
the authors of the study. “You can find its cousins in caves, on your
skin, at the bottom of the ocean and just about anywhere. What is
different, in this case, is its unique qualities that allow it to grow
in Mars-like conditions.”
In
a laboratory setting at room temperature and with normal oxygen levels,
the scientists demonstrated that the microbes can consume organic
material (sugar). But when the researchers removed the organic material,
reduced the temperature to near-freezing, and lowered the oxygen
levels, the microbes began to use the iron within olivine—a common
silicate material found in volcanic rocks on Earth and on Mars—as its
energy source.
“This
reaction involving a common mineral from volcanic rocks just hasn’t
been documented before,” said Martin Fisk, a professor in OSU’s College
of Earth, Ocean, and Atmospheric Sciences and an author on the study.
“In volcanic rocks directly exposed to air and at warmer temperatures,
the oxygen in the atmosphere oxidizes the iron before the microbes can
use it. But in the lava tube, where the bacteria are covered in ice and
thus sheltered from the atmosphere, they out-compete the oxygen for the
iron.
“By mimicking those conditions, we got the microbes to repeat that behavior in the laboratory,” Fisk added.
Amy Smith and Radu Popa collect samples of ice with basalt chips containing olivine from a lava tube in Oregon ‘s Cascade Mountains. Photo: Jane Boone |
The
microbes were collected from a lava tube near Newberry Crater in
Oregon’s Cascades Mountains, at an elevation of about 5,000 feet. They
were within the ice on rocks some 100 feet inside the lava tube, in a
low-oxygen, near-freezing environment. Scientists, including Fisk, have
said that the subsurface of Mars could have similar conditions and
harbor bacteria.
In
fact, Fisk has examined a meteorite originating from Mars that
contained tracks—which could indicate consumption by microbes—though no
living material was discovered. Similar tracks were found on the rocks
from the Newberry Crater lava tube, he said.
“Conditions
in the lava tube are not as harsh as on Mars,” Fisk said. “On Mars,
temperatures rarely get to the freezing point, oxygen levels are lower
and at the surface, liquid water is not present. But water is
hypothesized to be present in the warmer subsurface of Mars. Although
this study does not exactly duplicate what you would find on Mars, it
does show that bacteria can live in similar conditions.
“We
know from direct examination, as well as satellite imagery, that
olivine is in Martian rocks,” Fisk added. “And now we know that olivine
can sustain microbial life.”
The
idea for exploring the lava tube came from Radu Popa, an assistant
professor at Portland State University and lead author on the paper.
Popa used to explore caves in his native Romania and was familiar with
the environmental conditions. Because lava tubes are a sheltered
environment and exist on both Earth and Mars, Popa proposed the idea of
studying microbes from them to see if life may exist – or could have
existed – on the Red Planet.
“When
temperatures and atmospheric pressure on Mars are higher, as they have
been in the past, ecosystems based on this type of bacteria could
flourish,” Popa said. “The fingerprints left by such bacteria on mineral
surfaces can be used by scientists as tools to analyze whether life
ever existed on Mars.”
