Wow, good Astronomy and Astrophysics this month (“July,” vol. 687).
Woitke et al. study the smallest “asteroids” of all: the calcium-aluminum rich inclusions. CAIs, which turn solid at very high temperatures, then form durable ‘rock droplets’, are widely held to be the first mineral deposits to have formed from the Solar Nebula as it cooled. Condensation of the CAIs, then, are used to mark the “birthday” of our Solar System, and likely other Systems.
Ligterink et al. tackle an open question: what drives comet activity? Rosetta tantalized us but never gave the actual answer. They use Rosetta data- on Churyumov-Gerasimenko’s noble gas fraction- to figure at least a fraction of the question.
New meteor shower! Meteor showers are remnants of comet activity (and, less often, astero-comets); the various properties of meteors (starting with their trajectories), per Janches et al., tell us of some parent comet. Or “comet.”
Speaking of characterizing the asteroids: what is their internal structure? NEAR Shoemaker tantalized us with Mathilde, apparently a “rubble pile” body; the Hayabusas studied such ‘piles’ further. Now we have DART data (soon with Hera data); this may be needed for Earth threats.
But back to meteors: Shober et al. draw inferences between some common comets (the dynamical family of comets linked to Jupiter’s gravitational influence) and likely meteors from them.
To circularize: impactors and their target/product rubble mark the mundane histories of the Solar System; Vesta, Ryugu, and Bennu have clear ‘contaminants’ from other bodies. What do target/product rubbles of metal-rock impacts look like? What might Psyche see in 2029?
…and speaking of endless characterization of asteroids, Cellino et al. complement Carry et al., with data from the Gaia mission. Gaia tirelessly sweeps the skies with a nontrivial telescope; the Gaia dataset (rather, sets… hang on, craft!) will be combed through and through for decades.
…and Lemos et al. complement Ligterink et al. Rather than hypervolatiles, they consider clumps and hyperactivity. Some comet activity is simple mass loss, and some is ‘meta-activity’. Comets shed clumps which may themselves show activity- fragmenting into lesser dust structures.
Which brings us to Shubina et al./Barghini et al. Dust astronomy seems trivial, by human standards: people on the street can’t grok dust, which is at inhuman scale. But various dusts- fine grains and particles, and their clumps, plus the micrometeorites- outweight the meteorites that fall to Earth, and by over an order of magnitude. And dust is more likely to preserve the volatiles from its parent body, compared to macro-meteorites, which enter like a slam dunk, not a badminton bird. Macro-meteorites punch into our atmosphere, heating themselves. Collecting and studying space dust is then one of the more productive avenues we have on comets… and “comets.”
A very few of those small bodies actually orbit the Sun “backwards” (retrograde). This includes, in 3-D, orbits that aren’t in the same plane as the planets (the ecliptic), but skewed completely, like a highway cloverleaf. What of these Solar System deviants? Wlodarczyk has some data.
Before we close: there’s no escaping artificial intelligence these days. One application is multidimensional reconstruction/constructs, such as DALL·E. Another is Asteroid-NeRF, except it starts with controlled, certifiable, deterministic asteroid data, not “the ‘Net.”
Whew.