Clark is the mission asteroid scientist for OSIRIS-REx, a spacecraft that will map and take a sample from in order to determine what the asteroid is made of and whether its orbit is likely to evolve to be on course to hit Earth. In 2010, a group of scientists determined that Bennu could have a relatively high probability of impacting Earth between the years 2169 and 2199.
鈥淭丑别 will give us data to help more precisely predict Bennu鈥檚 orbit and, in general, devise strategies to mitigate possible impacts between Earth and other asteroids,鈥� said Clark.
As mission asteroid scientist, Clark is responsible for managing three of OSIRIS-REx鈥檚 experiments: thermal analysis, spectral analysis and visual color imaging analysis during the global survey of Bennu. Thermal analysis is key to predicting where Bennu鈥檚 orbit will take it. Known as the Yarkovsky effect, the absorption and re-emission of thermal energy by an asteroid exerts a force that changes its flight.
鈥淲e鈥檙e going to send a thermal emission spectrometer and it鈥檚 going to measure the temperature of the asteroid鈥檚 surface globally at seven different times of day,鈥� said Clark. 鈥淲e鈥檒l analyze the changes in temperature with time, and that鈥檚 going to tell us the thermal inertia of the surface 鈥� how quickly or slowly the surface cools off. This, in turn will tell us how the thermal properties of Bennu affect the small forces that can change its orbit over time.鈥�
Besides determining with greater precision whether Bennu is likely to hit Earth, the OSIRIS-REx mission also aims to shed light on the formation of Earth鈥檚 solar system by take a sample from the asteroid鈥檚 surface. It is the first NASA mission to collect a sample from an asteroid and return it to Earth.
Asteroids are remnants of the building blocks of the planets and can contain organic materials, water and metals. Asteroids that have landed on Earth have been found to contain diamonds and even amino acids that may have been the precursors to life on our planet. Bennu is a very darkly colored asteroid, suggesting that it is rich in carbon compounds.
鈥淥ur hope is that because this asteroid seems to be more carbon-rich than anything currently in our collection, it may represent an unsampled meteorite type and will tell us something new about the solar system,鈥� said Clark. 鈥淔inding new material that we鈥檝e never seen before gives us strong constraints on models of solar system origin, and that鈥檚 what we want! We want to learn more about the formation of the solar system and the origin of planets because many planets may have started as asteroids.鈥�
During the mission鈥檚 development stage, Ithaca College students assisted Clark with preparations for her experiments. Linda Crandall 鈥�16 used data from past asteroid missions to correct distortions to spectral readings caused by changes in the angle at which the asteroid is viewed.
鈥淭丑别 goal was to be prepared with a 鈥榖est model鈥� ahead of time so we do not need to spend time deciding when we get data from Bennu,鈥� said Crandall.
As part of her work, Crandall attended a science team meeting near the NASA Jet Propulsion Laboratory in Pasadena, California, where she met with scientists collaborating on the mission. She is now pursuing a doctorate in physics at the University of Rochester and hopes to work in a national laboratory.
OSIRIS-REx鈥檚 34-day launch window from Cape Canaveral opens on September 8, and the spacecraft will take approximately two years to reach Bennu. Visual observations and spectral analysis will be used to determine the ideal spot from which to take a sample, with OSIRIS-REx performing a touch-and-go maneuver and using an extendable arm to collect loose rocks and soil from the asteroid鈥檚 surface. The spacecraft will continue to follow Bennu as it orbits the Sun, finally completing its seven-year journey and returning to Earth with the sample for analysis in 2023.
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