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E. G. Rivera-Valentín

Publications and source records attributed to E. G. Rivera-Valentín.

2 recordsLinked to original sources

Community need for an Astrobiology Sample Repository and Sample Reference Suite

As we prepare for the next planetary mission charged with finding life beyond Earth, the Astrobiology community must continue to improve its understanding of what constitutes a biosignature, through the use of planetary analog samples. The study of these collected and generated samples is expanding our knowledge of what constitutes habitable environments, what life is capable of, and importantly, how to make biosignature detections within compositionally complex samples - aiding in the development of life detection instrumentation. And yet the full potential of these samples remains untapped. While the Astrobiology community possesses an incredible inventory of planetary analog samples, some incredibly precious, these are scattered across the country in individual freezers with varying degrees of documentation, curation practices, and contamination control. We, as a community, need to change the status quo of how we approach planetary analog research. One of the biggest actions we could take over the next 10 years to change that paradigm would be the creation of a sample repository for Astrobiology relevant materials, providing a centralized, well-curated, wealth of precious samples for the community. Such a collection would create a framework for material and meta-data submission that minimizes burden on the individual PIs, satisfying open data requirements; it would facilitate biosignature research, and aid in the creation of a robust life detection framework; support the development of a standardized sample reference suite for life detection instrumentation; and finally, aid in the development of techniques to be used for future sample return endeavors.

astro-ph.IM↗

Shaking and Tumbling: Short- and Long-Timescale Mechanisms for Resurfacing of Near-Earth Asteroid Surfaces from Planetary Tides and Predictions for the 2029 Earth Encounter by (99942) Apophis

Spectral characterization of near-Earth asteroids (NEAs) has revealed a continuum of space-weathered states for the surfaces of S-complex NEAs, with Q-class NEAs, an S-complex subclass, most closely matching the un-weathered surfaces of ordinary chondrite meteorites. Dynamical calculations of the orbital evolution of S-complex NEAs revealed that Q-class NEAs tend to have close encounters with terrestrial planets, suggesting that planetary tides may play a role in refreshing NEA surfaces. However, the exact physical mechanism(s) that drive resurfacing through tidal encounters and the encounter distance at which these mechanisms are effective, has remained unclear. Through the lens of the upcoming (99942) Apophis encounter with Earth in 2029, we investigate the potential for surface mobilization through tidally-driven seismic shaking over short-timescales during encounter and subsequent surface slope evolution over longer-timescales driven by tumbling. We perform multi-scale numerical modeling and find that the 2029 encounter will induce short-term tidally-driven discrete seismic events that lead to high-frequency (>0.1 Hz) surface accelerations that reach magnitudes similar to Apophis' gravity, and that may be detectable by modern seismometers. It is still unclear if the shaking we model translates to widespread particle mobilization and/or lofting. We also find there will be a significant change in Apophis' tumbling spin state that could lead to longer-term surface refreshing in response to tumbling-induced surface slope changes. We propose that through these mechanisms, space-weathered S-class asteroid surfaces may become refreshed through the exposure of unweathered underlying material. These results will be tested by the future exploration of Apophis by NASA's OSIRIS-APEX.

astro-ph.EP↗