Lots of stuff (as one might expect from the title) in PSJ (Planetary Science Journal):
Rivera-Valentin, E. G. et al. Radar Circular Polarization Ratio of Near-Earth Asteroids: Links to Spectral Taxonomy and Surface Processes art 232 ad7df1
Poston, M. J. et al. Experimental Examination of Brine and Water Lifetimes after Impact on Airless Worlds art 233 ad696a
Mahjoub, A. et al. Dual Sources of S2 Observed in Comet 67P: Insights from Comparing ROSINA Measurements and Laboratory Simulations art 234 ad7d86
Deleon, A. P. et al. Physical and Mutual Orbit Characteristics of Near-Earth Binary
Asteroid (163693) Atira art 235 ad7814
Vincent, J-B. et al. Macroscale Roughness Reveals the Complex History of Asteroids Didymos and Dimorphos art 236 ad7a01
Stickle, A. M. et al. 2024 Tour of Asteroids for Characterization Observations (TACO): A Planetary Defense Asteroid Tour Concept art 237 ad7a6c
Myers, S. A. et al. 2024 Inconsistencies in Simple Thermal Model Results for Near-Earth Asteroids between Infrared Telescope Facility Spex and NEOWISE Data art 238 ad8157
RIP Arecibo, but radar goes on. The specifics of radar (like polarization, and its modulation) already told us of the “soil” (regolith) properties of surfaces in the Solar System. In addition to regolith size, Rivera-Valentin tell of other results, including asteroid typing from the regolith roughness.
Hmmm, brine on airless worlds, whatever could they be talking about? Why, Ceres, of course! Or, at minimum, other Main-Belt Comets, of which there are several (possibly including Vesta). It was the MBCs that prompted the IAU to change “asteroid” and “comet” to “small solar system body (SSSB)” in 2006.
Regarding small solar system bodies, the term “volatiles” includes not just water, but sodium and sulfur as low-melting-point ‘minerals.’ Sulfur is not rare at all, cosmically, and as seen in meteorites. It stands that most asteroids, with primitive compositions and low exposures to heat, should be fairly sulfur-rich. Those other small solar system bodies, comets, would also be expected to have at least as much S, and in multiple, reduced forms. (We have seen sodium tails, streaming from comets along with the other, greater tails.) Mahjoub et al. test this assumption.
When an SSSB is a binary (one natural satellite, or sometimes two equal bodies), we can deduce things from their orbit range and timing. Although binaries among the Near-Earth Objects are not that rare, we should study them whenever we can. (163693) Atira- the namesake of the Atira asteroids- is one such multi-NEO system. Since Atira (and the Atiras) are close to the Sun in the sky, it (they) are difficult to observe using ground-based telescopes. Such targets are in the dawn/dusk sky, and often glared out by the Sun. Deleon et al. did the legwork, to catch (163693) Atira and its satellite at the times when viewing geometry was favorable.
Ever since Hayabusa at Itokawa, we’ve been trying to deduce the internal structures of asteroids. It appears Itokawa- though largely a rubble-pile object- still has nontrivial chunks in it, giving it its lobed shape. (Even before then, there was speculation that Gaspra, as seen by Galileo, was regolith piled over some slab, which is how it had a slab-ish shape overall.) This work continues at Didymos/Dimorphos. As seen by DART, the two bodies are mostly rubble, but with signs of structure. What signs, and what structure, ask Vincent et al.?
There’s no shortage of asteroid mission concepts, as I had noted. NEOs are in accessible orbits, with low propellant requirements and thus low launcher issues. Since there are tens of thousands of NEOs in total, there may be chances to string together two or more, and form a multi-mission. Galileo did this, NEAR Shoemaker did this, Hayabusa2 and Lucy are now doing this, and Stickle et al. propose doing it again. Stardust even managed this with comets, whose orbits are inconvenient and less accessible.
And now let us consider Myers et al. Sending probes is all well and good, but there’s no way we can send tens of thousands, even on multi-flyby missions. Some asteroids- yes, NEOs too- will remain astronomical (point) objects. So how do we deduce the properties of that point? For many, the answer is infrared telescopes. Comparing the optical and infrared brightnesses can be used to determine the object size- can. We’ve known, for a while now, that the infrared estimate isn’t a simple relationship with size. There are other, lesser factors, and Myers et al. go into them. I’m not saying that using the infrared is futile, but I (and Myers et al.) caution against too many assumptions.