Aerospace and Mechanical Engineering Seminar Dr. Erik Asphaug Professor Planetary Science & Lunar and Planetary Laboratory University of Arizona [email protected]
Near-Earth Space: Targets of Exploration
Abstract: Near-Earth space is the domain of asteroids and other objects (NEOs) that orbit the Sun and sometimes come very close to Earth. It also includes the Moon and cislunar space, and by extension of exploration I’d include Phobos and Deimos, the asteroid-like satellites of Mars. One might define it loosely as the realm of potential human expansion in the coming century. One thing these bodies have in common, is they are airless. This makes their surface materials quite different from the stuff of ordinary geological experience; for instance liquid water can’t exist. Another thing in common is their low gravity, which renders them bizarre in their behavior. The Moon is a comparative giant and thus the most familiar – the Main Belt of asteroids between Mars and Jupiter, the source population of most NEOs, is only 5% as massive. The Moon’s surface gravity is thousands of times greater than the small bodies that have been explored by recent spacecraft missions, so in that sense is 1000x more earthlike.
Small body exploration is experiencing a heyday; after it drops off the samples it acquired at 900-m diameter Ryugu, the Hayabusa2 mission could rendezvous with an asteroid only 30-m diameter that is spinning every ten minutes – any loose materials would be flung into space. We’ve never seen anything like that. China is planning a sample return mission to another of these tiny, fast-rotating bodies, this time an NEO that is temporarily orbiting the Earth, of importance for many reasons. After the OSIRIS-REx mission drops off samples from 500-m asteroid Bennu, it too has the resources for an extended mission, in this case to Apophis, the “doomsday asteroid” that briefly had a significant chance of impact on April 13, 2029 but will instead miss by five Earth-radii. NASA’s Lucy, Psyche and Janus missions are preparing for launch, and so is DART, the impactor mission to be launched next year, to test the kinetic deflection of a potentially-hazardous asteroid. Then there is ESA’s Hera mission, a multi-spacecraft rendezvous to follow-up and see what happened after DART impacted, and the Japanese MMX mission to the Martian satellites, the first ever mission to these bodies.
My talk will focus on the objects in near-Earth space, summarize just a few of the ongoing mission efforts, and describe some of our own ideas for low-cost missions, from Discovery-class (Comet Radar Explorer) to CubeSats and small surface robots. I will try to leave ample time for questions.
Bio: Prof. Asphaug studies planet and satellite formation, including giant impacts such as that which formed the Moon. The ensuing diversity of planets is the subject of When the Earth Had Two Moons (HarperCollins, 2019). He also studies asteroids, comets and satellites, hoping to understand their formation, evolution, geology and morphology. He has served on the NAS Committee on Astrobiology and Planetary Science since 2017. He participates in laboratory and theoretical research into the physics of meteorites, and various topics related to Mars, the Moon, and satellites of giant planets. His mission involvement includes Galileo, LCROSS, OSIRIS-REx, DART, Psyche, MMX and Hera. He is PI of the Comet Radar Explorer mission concept that has competed twice in NASA Discovery.
Thursday, October 1, 2020 at 4:00 P.M. Zoom Link: Email [email protected]