Asteroids: is there anything they can’t do? The NASA Fundamental Physics Workshop was this week, in San Diego. Among the topics was Graham et al.’s concept for asteroids as a physics instrument:
Day 2 (Wed), Session 7, 4:25: Fundamental Physics with Asteroids – Peter Graham
“We propose the use of ~1 – 10 km stony asteroids as inertial test masses for a variety of fundamental physics applications such as…”
On the ground, we already have LIGO, VIRGO, and others in construction. In space, the future LISA (now partially tested) will cover a different range, for those gravitational waves coming from different sources. By observing two pulsars, we also get gravitational waves, from yet a different range of wavelengths. There exists a certain wavelength range where a decent-sized asteroid makes (with a base station on it) a gravitational-wave detector. If you don’t find Graham credible or whatever, then try the coauthors:
Physical Review D
Fedderke, M. A. Graham, P. W. Rajendran, S. Gravity gradient noise for astero… vol. 103, article 103017
.103.103017
Fedderke, M. A. Graham, P. W. Rajendran, S. Asteroids for μHz gravitational-wave d… v.105 art.103018 .105.103018
Fedderke, M. A. Mathur, A. Asteroids for ultralight dark-photon dark-matter detectio… v.107 art.043004 .107.043004
Asteroids, Comets, Meteors Conference 2023
Rajendran, S. Graham, P.W. Fedderke, M. A. Asteroids for Micro-Hz Gravitational Wave Detection #2086
I will say, though: these investigators make the assumption that asteroids are geologically (pygmaiologically?) stable, so they won’t disturb the readings. Not to regurgitate or parrot Empire Strikes Back (hardly a goldmine for small-body science), but one cannot simply make the stability assumption offhand. On a sufficiently-short timescale, sure. But rubble-pile bodies experience granular motion on some level; we saw evidence of this on Itokawa, and more on Ryugu and Bennu. The investigators use a picture of Eros, and explicitly name “Eros.” To their credit, Eros is not a rubble-pile, and makes a better base station. However, they go on and show a rubble-pile object as their second ranging station.
And to top it off, the waves go in the other direction. A gravity detector can be used to spot large masses going by; large masses like… asteroids! Among other proposals:
2024 APS Spring Meeting (Eastern Great Lakes Section)
Ford, N. Detection of Near-Earth Asteroids Using the LISA Spacecraft E01.00012
“this project can contribute to filling NASA’s Small-Body Database and give LISA the secondary purpose of detecting asteroid threats to Earth.”
Smarter people than I am tackling the issue from other directions. Human progress occurs when multiple such directions can pick up the ball if another drops it.