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| An artist concept featuring NASA's Curiosity rover [IMAGE: NASA/JPL-Caltech] |
Pasadena, California: Observations of wind patterns and natural radiation patterns
on Mars by NASA's Curiosity rover are helping scientists better understand the
environment on the Red Planet's surface.
Researchers using the
car-sized mobile laboratory have identified transient whirlwinds, mapped winds
in relation to slopes, tracked daily and seasonal changes in air pressure, and
linked rhythmic changes in radiation to daily atmospheric changes. The
knowledge being gained about these processes helps scientists interpret
evidence about environmental changes on Mars might have led to conditions
favorable for life.
During the first 12
weeks after Curiosity landed in an area named Gale Crater, an international
team of researchers analyzed data from more than 20 atmospheric events with at
least one characteristic of a whirlwind recorded by the Rover Environmental
Monitoring Station (REMS) instrument. Those characteristics can include a brief
dip in air pressure, a change in wind direction, a change in wind speed, a rise
in air temperature or a dip in ultraviolet light reaching the rover. Two of the
events included all five characteristics.
In many regions of
Mars, dust-devil tracks and shadows have been seen from orbit, but those visual
clues have not been seen in Gale Crater. One possibility is that vortex
whirlwinds arise at Gale without lifting as much dust as they do elsewhere.
"Dust in the
atmosphere has a major role in shaping the climate on Mars," said Manuel
de la Torre Juarez of NASA's Jet Propulsion Laboratory (JPL) in Pasadena,
Calif. He is the investigation scientist for REMS, which Spain provided for the
mission. "The dust lifted by dust devils and dust storms warms the
atmosphere."
Dominant wind
direction identified by REMS has surprised some researchers who expected slope
effects to produce north-south winds. The rover is just north of a mountain
called Mount Sharp. If air movement up and down the mountain's slope governed
wind direction, dominant winds generally would be north-south. However,
east-west winds appear to predominate. The rim of Gale Crater may be a factor.
"With the crater
rim slope to the north and Mount Sharp to the south, we may be seeing more of
the wind blowing along the depression in between the two slopes, rather than up
and down the slope of Mount Sharp," said Claire Newman, a REMS
investigator at Ashima Research in Pasadena. "If we don't see a change in
wind patterns as Curiosity heads up the slope of Mount Sharp -- that would be a
surprise."
REMS monitoring of
air pressure has tracked both a seasonal increase and a daily rhythm. Neither
was unexpected, but the details improve understanding of atmospheric cycles on
present-day Mars, which helps with estimating how the cycles may have operated
in the past.
The seasonal increase
results from tons of carbon dioxide, which had been frozen into a southern
winter ice cap, returning into the atmosphere as southern spring turns to
summer. The daily cycle of higher pressure in the morning and lower pressure in
the evening results from daytime heating of the atmosphere by the sun. As
morning works its way westward around the planet, so does a wave of
heat-expanded atmosphere, known as a thermal tide.
Effects of that
atmospheric tide show up in data from Curiosity's Radiation Assessment Detector
(RAD). This instrument monitors high-energy radiation considered to be a health
risk to astronauts and a factor in whether microbes could survive on Mars' surface.
"We see a
definite pattern related to the daily thermal tides of the atmosphere,"
said RAD principal investigator Don Hassler of the Southwest Research
Institute's Boulder, Colo., branch. "The atmosphere provides a level of
shielding, and so charged-particle radiation is less when the atmosphere is
thicker. Overall, Mars' atmosphere reduces the radiation dose compared to what
we saw during the flight to Mars."
The overall goal of
NASA's Mars Science Laboratory mission is to use 10 instruments on Curiosity to
assess whether areas inside Gale Crater ever offered a habitable environment
for microbes.