Dr. Ashwin Vasavada, Planetary Scientist at the Jet Propulsion Laboratory in Pasadena, California and Deputy Project Scientist for the Mars Science Laboratory mission at NASA's Jet Propulsion Laboratory talks to Kal Kaur, Editor for AZoSensors on the sensor technology inside NASA’s Curiosity Rover.
KK - NASA’s Curiosity rover is helping scientists observe wind patterns and natural radiation patterns on the surface of Mars. Can you give the audience a brief introduction to the Curiosity rover and its main objectives for this mission?
AV - The Mars Science Laboratory mission is using the Curiosity rover, with its 10 science instruments, to investigate an intriguing area called Gale Crater. We're trying to figure out whether the area has ever offered environmental conditions favorable for life. Gale Crater is a huge basin about 96 miles in diameter, with a 3-mile-tall layered mountain in the center.
Artist's conception of NASA's Curiosity Mars Rover investigating the composition of Martian rock. The rover is equipped with a huge array of sensors and analysis equipment, enabling it to send back a huge amount of new data about the red planet.
KK - Can you describe the sensor technology in the car-sized laboratory that is helping identify transient whirlwinds, in relation to slope and seasonal changes in air pressure and radiation changes?
AV - One of our instruments, the Rover Environmental Monitoring Station, or REMS, monitors atmospheric pressure, wind speed and wind direction. Pressure is measured using capacitance-based sensors developed by Vaisala. Wind speed and direction are sensed using a number of hot-film anemometers located on two short booms attached to the rover's mast. REMS was provided to Curiosity by Spain.
The energetic particle environment at the rover is monitored using a separate instrument, the Radiation Assessment Detector, or RAD. RAD is able to characterize several types of particles over a wide energy range, including galactic cosmic rays, solar energetic particles, and secondaries produced in the atmosphere or subsurface. It uses three solid-state detectors and a cesium iodide calorimeter. An additional scintillating plastic channel is used together with the calorimeter and an anticoincidence shield to detect and characterize neutrons and gamma rays.
KK - How are the sensors in the Curiosity rover helping us understand the nature of Mars and how its atmosphere is evolving?
AV - The REMS and RAD sensors are monitoring changes on daily and longer cycles, recording current conditions as well as seasonal patterns. In addition, Curiosity has a tunable laser spectrometer that analyzes the abundance and isotope ratios of atmospheric carbon dioxide, water, and methane. Isotope ratios of the present atmosphere support the hypothesis that Mars once had a more massive atmosphere.
KK - What challenges can you expect for the Curiosity rover on Mars? Are there any environmental changes that you think could compromise Curiosity’s environmental monitoring station?
AV - The rover's electronics face challenges of very large daily cycles in temperature, but the equipment is designed and tested to give us confidence in its performance over the life of the mission. So far REMS has provided over two million measurements.
KK - How has the REMS monitoring of air pressure tracked seasonal increase and daily rhythm and what does this tell us about the atmospheric cycles on Mars?
AV - Atmospheric pressure varies in a daily tidal pattern and also has been increasing week-to-week in a seasonal pattern. 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. The seasonal increase results from literally tons of carbon dioxide, which had been frozen into a southern winter ice cap, returning into the atmosphere as southern spring turns to summer.
Sensors on two finger-like mini-booms extending horizontally from the mast of NASA's Mars rover Curiosity monitor wind speed, wind direction and air temperature.
KK - How does Curiosity’s Radiation Assessment Detector (RAD) work to show impact of atmospheric tides on Mars?
AV - Both the amount and nature of the measured radiation changes with atmospheric pressure. The atmosphere shields the surface from some energetic particles, but also results in secondaries produced by collisions with atmospheric molecules.
KK - The RAD has been used to detect radiation levels that are high enough to be a hazard to astronauts. Does this challenge the possibility of microbial organisms being able to survive on Mars?
AV - Given Mars' thin atmosphere and lack of a planetary magnetic field, both energetic particles and ultraviolet light reach the surface in greater levels than on Earth and pose hazards to potential life. If life exists today on Mars, perhaps it is relegated to subsurface habitats. But even if life on Mars remains elusive, RAD's measurements will help the design of future human missions to Mars.
KK - There has recently been news about damage to a sensor on the robot’s weather station that provides readings about the wind conditions on Mars. Will damage to this sensor and any other sensors integrated into this robot degrade measurements?
AV - The science team has developed ways to monitor wind direction in spite of the damaged sensor. It will be fascinating to relate the winds to the geology we see as we drive towards the 3-mile-high Mount Sharp. Much of Mars' current geology is shaped by wind, including the extensive dune fields encircling the mountain.
About Ashwin Vasavada
Dr. Ashwin Vasavada is a planetary scientist at the Jet Propulsion Laboratory in Pasadena, California. He is the Deputy Project Scientist on the Mars Science Laboratory mission with its Curiosity rover, helping to lead the international team of over 400 scientists.
His research interests include the climate history of Mars, the weather on Jupiter and Saturn, and the possibility of ice at the poles of the Moon and Mercury. He has participated in the operation and analysis of data from several NASA spacecraft missions, including the Galileo mission to Jupiter and the Cassini mission to Saturn.
A Californian all his life, he holds a B.S. in Geophysics from UCLA and a Ph.D. in Planetary Science from Caltech.
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