June 8th 05, 07:25 PM
http://www.napa.ufl.edu/2005news/marsalgae.htm
TRACES OF STOWAWAY EARTH ALGAE COULD SURVIVE ON MARS, STUDY FINDS
Writer: Carolyn Gramling, (352) 392-0186,
Source: Andrew Schuerger, (321) 861-3478,
May 17, 2005
GAINESVILLE, Fla. --- Some hardy Earth microbes could survive long
enough on Mars to complicate the search for alien life, according to a
new study co-authored by University of Florida researchers.
Though scientists looking for life on Mars worry about contamination
from stowaway spores clinging to spacecraft, the inhospitable Martian
environment is actually an effective sterilizing agent: The intense
ultraviolet rays that bombard the Martian surface are quickly fatal to
most Earth microbes. However, the new study shows that at least one
tough Earth species, a type of blue-green algae called
Chroococcidiopsis, could live just long enough to leave a biological
trace in the Martian soil - creating a potential false positive.
The study appears in the current issue of the journal Astrobiology and
was co-authored by Charles Cockell of the British Antarctic Survey and
UF research assistant professor Andrew Schuerger, a Mars astrobiologist
and plant pathologist at UF's Institute of Food and Agricultural
Sciences. Schuerger is one of several UF researchers associated with
the
Kennedy Space Center's Space Life Sciences Laboratory, where he
investigates how Earth microbes might survive, grow and adapt in
simulated Martian conditions.
"It's very possible that we could send viable microorganisms to Mars
and
then bring some of those same Earth bugs back with us," Schuerger said.
The researchers examined a dry-tolerant and radiation-resistant algae
that thrives in Earth's most extreme conditions, from the hot, arid
Negev desert in Israel to the frigid Antarctic Ross Desert. This
bacterium has not been found on the surfaces of spacecraft, but it
represents a worst-case scenario for scientists.
"The only way to find out (if there's life on Mars) is by going there
and studying it, yet we take with us the potential to contaminate our
own studies," said John Rummel, NASA's current Planetary Protection
Officer. NASA created the Planetary Protection Office to safeguard
against transferring potentially harmful organisms to or from Earth
during space exploration.
"It's the biological Heisenberg principle," Rummel added. "Can we do
the
studies without contaminating what we're looking at? So we have to have
some idea of whether or not Earth life is likely to survive (on other
planets)."
To test the limits of the algae's endurance, the researchers subjected
it to a simulated Martian atmosphere, re-created within a 5-foot-long
stainless steel barrel-shaped chamber.
On Mars, average global temperature is -78 degrees Fahrenheit,
atmospheric pressure is one-hundredth of the Earth's and UV rays
striking the surface are three times as intense as on the
ozone-protected Earth - enough to produce a severe sunburn on exposed
skin in minutes. Of these harsh conditions, the UV rays are the most
powerful sterilizing agent, Schuerger said.
The researchers found that when exposed to the full spectrum of these
rays, 99.9 percent of the algae in the chamber died within five minutes
- significant when compared with the survival time of other microbes
exposed to the same conditions: 15 seconds. However, the algae also
left
chemical traces of their existence that were detectable for several
more
hours. Those "biosignatures" included component molecules such as
chlorophyll and the measured activity of enzymes involved in cell
membrane formation. Enzyme activity persisted for an hour, while traces
of chlorophyll remained for up to four hours.
"This demonstrates that looking for biogenic signatures alone will
complicate the process of looking for life," he said. "You have to do
both, you have to do a number of different procedures, and they have to
complement one another."
The algae also managed to survive when it was shielded from the direct
onslaught of UV rays by a millimeter-thick layer of sand or rock. Such
a
scenario could occur if a robot lands on the Martian surface and its
pads sink immediately into the sand, Schuerger said. However, though
buried microbes may survive for some period of time, they are still
subject to Mars' low atmospheric pressure, high aridity and temperature
extremes. Under those conditions, they wouldn't necessarily grow or
reproduce and are therefore unlikely to pose an ongoing contamination
threat, he added.
Rummel agreed. "You might have a very lonely cyanobacterium waiting for
something to happen."
The paper's other authors include Daniela Billi of the University of
Rome; E. Imre Friedmann of NASA's Ames Research Center; and Dr. Corinna
Panitz of the German Aerospace Center in Koln. Space Life Sciences
Center.
-30-
TRACES OF STOWAWAY EARTH ALGAE COULD SURVIVE ON MARS, STUDY FINDS
Writer: Carolyn Gramling, (352) 392-0186,
Source: Andrew Schuerger, (321) 861-3478,
May 17, 2005
GAINESVILLE, Fla. --- Some hardy Earth microbes could survive long
enough on Mars to complicate the search for alien life, according to a
new study co-authored by University of Florida researchers.
Though scientists looking for life on Mars worry about contamination
from stowaway spores clinging to spacecraft, the inhospitable Martian
environment is actually an effective sterilizing agent: The intense
ultraviolet rays that bombard the Martian surface are quickly fatal to
most Earth microbes. However, the new study shows that at least one
tough Earth species, a type of blue-green algae called
Chroococcidiopsis, could live just long enough to leave a biological
trace in the Martian soil - creating a potential false positive.
The study appears in the current issue of the journal Astrobiology and
was co-authored by Charles Cockell of the British Antarctic Survey and
UF research assistant professor Andrew Schuerger, a Mars astrobiologist
and plant pathologist at UF's Institute of Food and Agricultural
Sciences. Schuerger is one of several UF researchers associated with
the
Kennedy Space Center's Space Life Sciences Laboratory, where he
investigates how Earth microbes might survive, grow and adapt in
simulated Martian conditions.
"It's very possible that we could send viable microorganisms to Mars
and
then bring some of those same Earth bugs back with us," Schuerger said.
The researchers examined a dry-tolerant and radiation-resistant algae
that thrives in Earth's most extreme conditions, from the hot, arid
Negev desert in Israel to the frigid Antarctic Ross Desert. This
bacterium has not been found on the surfaces of spacecraft, but it
represents a worst-case scenario for scientists.
"The only way to find out (if there's life on Mars) is by going there
and studying it, yet we take with us the potential to contaminate our
own studies," said John Rummel, NASA's current Planetary Protection
Officer. NASA created the Planetary Protection Office to safeguard
against transferring potentially harmful organisms to or from Earth
during space exploration.
"It's the biological Heisenberg principle," Rummel added. "Can we do
the
studies without contaminating what we're looking at? So we have to have
some idea of whether or not Earth life is likely to survive (on other
planets)."
To test the limits of the algae's endurance, the researchers subjected
it to a simulated Martian atmosphere, re-created within a 5-foot-long
stainless steel barrel-shaped chamber.
On Mars, average global temperature is -78 degrees Fahrenheit,
atmospheric pressure is one-hundredth of the Earth's and UV rays
striking the surface are three times as intense as on the
ozone-protected Earth - enough to produce a severe sunburn on exposed
skin in minutes. Of these harsh conditions, the UV rays are the most
powerful sterilizing agent, Schuerger said.
The researchers found that when exposed to the full spectrum of these
rays, 99.9 percent of the algae in the chamber died within five minutes
- significant when compared with the survival time of other microbes
exposed to the same conditions: 15 seconds. However, the algae also
left
chemical traces of their existence that were detectable for several
more
hours. Those "biosignatures" included component molecules such as
chlorophyll and the measured activity of enzymes involved in cell
membrane formation. Enzyme activity persisted for an hour, while traces
of chlorophyll remained for up to four hours.
"This demonstrates that looking for biogenic signatures alone will
complicate the process of looking for life," he said. "You have to do
both, you have to do a number of different procedures, and they have to
complement one another."
The algae also managed to survive when it was shielded from the direct
onslaught of UV rays by a millimeter-thick layer of sand or rock. Such
a
scenario could occur if a robot lands on the Martian surface and its
pads sink immediately into the sand, Schuerger said. However, though
buried microbes may survive for some period of time, they are still
subject to Mars' low atmospheric pressure, high aridity and temperature
extremes. Under those conditions, they wouldn't necessarily grow or
reproduce and are therefore unlikely to pose an ongoing contamination
threat, he added.
Rummel agreed. "You might have a very lonely cyanobacterium waiting for
something to happen."
The paper's other authors include Daniela Billi of the University of
Rome; E. Imre Friedmann of NASA's Ames Research Center; and Dr. Corinna
Panitz of the German Aerospace Center in Koln. Space Life Sciences
Center.
-30-