The shattered S-type for a colony

C-types like Bennu and Ryugu are rubbly and soft. Even if we see them here, their origin is the grey zone; once Earth-trojan or Cruithne, their orbits are inclined and eccentric, making for a delta-V headache. At the 1 AU range where actually reachable, our main options are stony.

The Atíra class is difficult to see from Earth as they run close to daylight, like Venus; if stony, as many are, they might reflect light, but unless of Atira's massive volume, we don't see much more than a bright dot. So, I'll use higher-AU S-types for proxy. Like Didymus, which we've sent missions at.

Didymus is unrepresentative in one other way as helps us. Didymus is an oblate spheroid. That means it is composed like a fluid - and as not a differentiated body, it is made of rubble. Hence also why it's got a moon, from ejecta. Contrast solid and irregular Apophis: Didymus looks porous at 2400 ±300. And it is spinning already; we could spin it more.

Didymus has major radius 425m × minor 310m. This volume is ~2.34e8 m³, subRyugu. Let's start smaller. Posit a rock the physical size and shape of Bennu, but stony: 2023 EL, maybe. The size is 6.15e7 but density is 2400 for 1.5e11 kg.

The usable material in Bennu

David Jensen's mechanical math, in "Autonomous Restructuring of Asteroids into Rotating Space Stations", wasn't great. On looking into Jensen a bit more, I noticed Figure 2-1 using the same formula to deduce the "material" from the volume: divide by 4. So how's his material math?

Scrolling down, I saw Table 2-4 had Ryugu with type Cg; Atira of course being S. Table 3-6, though, has Ryugu as S; and Bennu also as S. Table 3-6 also has wildly different "packed" material than Figure 2-1; more like dividing by 1.95. What's up with that?

Absent a sample from Bennu direct, we know the densities of various carbonaceous chondrite. They have a range: 2.42 to 5.66 g/cm³; Mathilde at 1.3 ±0.2(!). Basically we know that the overall asteroid is rubble therefore porous; this "1.19" density is covering for at least half of the asteroid being empty space between rocks. And, for C's, the rocks are porous too.

To sum up, to get the usable material from Bennu begs the question. What needs doing is to get a sample. We're getting that in a few weeks. Jensen's "what-the-hell, divide by four" attitude might actually... work, as rule-of-thumb, if Bennu's rocks prove as porous as Bennu overall.

Now, if Bennu were instead S-type; that's different. Stony chondrites rarely get as porous as carbonaceous chondrites. Divide-by-four can work for Ryugu and Bennu; but not for Atira.

Sift

As we're looking at asteroid-colonies, Janhunen might start with pure regolith from our Moon. At some point even he must approach a free-floating asteroid. C-type (and some S-type) asteroids are rubble. Not all rubble is equal.

For our purpose, we're starting as light and as simple as possible. Janhunen finds a 90kT floating jumble for a colony. Miklavčič comes along with a bag to throw over it; then Jensen orders some robots to spin the bag (bro). Er. Where's the counterweight?

Miklavčič says, what counterweight. Big torus-section, evenly-distributed mass, it'll never get unbalanced to suddenly shift rotation at the wrong axis. LOL chaos isn't real. Although I am told that he can fix this by spinning a second big torus-section, of the same mass, in the opposite direction.

To the extent Miklavčič be justified (I'm a skeptic) I deem his design to apply only to the high-Jensen volumes. Given how little space-infrastructure we now own, we must start with Janhunen and low-Jensen volumes. Once we have that (small) colony, we don't want to share it with fifty-tonne hard silicates ("enstatite chondrites" as Earthers call 'em). You can't chip homes into them so easily; and they might not be great for mining straightway compared to the anhydrous glass which David Jensen liked. Much less, those valuable volatiles locked into the sooty bits.

I think Janhunen should like to sift the bag as it spins. The outer bag is, yes, some nanofibre as holds in the dirt and doesn't let too much regolith out. I suggest he cast additionally - internally - a net, with a good deal of tensile strength, designed to keep the biggest boulders apart from the rest.

Some of the larger rocks might be big useful chunks of hydrated coal, or platinum. If they exist - great! these can be plucked out from the rest of the larger rocks, by hand.

Once the thing is spinning good-enough that a good haul of large rocks have come up, those large rocks get dragged outside the others, and the rest of the rubble gets spun against that net of rocks.

It follows by the way that Janhunen's dumbbell is a very late stage of colonisation, if it be a stage at all. I'll have more to say on that.

American Avignon

This blog hasn't had cause to look into Scott Hahn since November 2020, when I was reading Politicizing the Bible. I am of mixed-mind on his wing of Catholic apologetic generally - and there is a wing, as the wider world is finding out. When word got out to my church that I am a sometime Semite, I got assigned to read Hahn's books on the Eucharist. I thought those were... good. PtB on the other hand was cowritten with Ben Wiker the intelligent-design dude.

Hahn is now in trouble for announcing his support for something the Texan bishop Joseph Strickland said (pdf). This bishop was warning his flock of the upcoming synod, which might run against historic Church teachings. Strickland is in that In Sinu Jesu wing with Viganò; which wing, Michael Lewis and I consider harmful. It happens that another bishop, more Italian-based, has a history of bizarre statements concerning the human family. As of 28 August Viganò will not address "Bergoglio" by his Papal name, and holds his Papacy as nominal. Smells like sedeprivatio-theory.

Lewis has asserted Hahn as being within this mire; upon receiving some slings-and-arrows, Lewis is now displaying himself like a pudgier Saint Sebastian. Which is not to say that Hahn's supporters are covering themselves in gloria, either.

I'll lay out my cards here: where the French-Enlightenment ran up against the thought of Hahn (and Wiker), three years ago my blog declared fraternité with the former. Hahn wrote as if, should the Pope preach that 2+2=5, those saying 2+2=4 are suspect with the ulterior motive of supporting a local tyrant against him. I haven't seen reason to change that assessment. Sean Swain Martin would appear to agree in his book, The American Pope. [UPDATE 9/6: I read the thesis it's based on. It's not good.]

I admit I do hold out hope for an Erasmian streak in Hahn. He is a former Protestant, and a man with deep intellectual curiosity; I feel he would prefer to strike a path more-independent than his publishers demand of him.

I hold out little similar hope for Lewis. I find his self-presentation to be a case of Crying Out As He Strikes You. I find it to be gamma.

I have to wonder about Brant Pitre and bishop Barron and others, where/when they'll enter this dispute.

STRICKLAND 11/11/23: He's done. Everyone needs to look to when their number comes up.

Jesus' stump-speech

The usual-suspects a couple days ago linked, by the usual-removes, to Eric Lyons, concerning how there exists no contradiction between Luke and Matthew about the Sermon on the Plain-or-Mount. Most of us wouldn't waste our time but, well. Maybe it was aliens?

The core is, as so-often, the Synoptic Problem - in this case a fairly-major agreement between Matthew and Luke, against Mark. The speech-variants and nearly all their content is/are absent from Mark. One question is whether Mark knew of a specific speech. I think... Mark did. But it wasn't the Sermon on the Mount (or plain).

The one fact we must base ourselves upon is that Luke was aware of earlier apostolic-memoirs - because Luke had told us so, in his first chapter. We can further deduce that at least one of these memoirs looked a lot like Mark. Another looked like Matthew. Farrer and lately Goodacre are fairly well-regarded by now.

So: Mark. Mark concentrates Jesus upon preaching the imminent kingdom of God; first by himself (1:14-15), later delegated to the apostles-in-training. If people wanted to hear what Jesus had to teach, those people went to the synagogues - at least at first (1:21f). Mark was more concerned to rush on to the Passion than to list every word and deed Jesus said/did, sure. Later Mark is rife with scenes in which the people gather around Jesus; he's got two (Mark 6:30f, 8:1f) in which Jesus must somehow feed them. For Mark that crowd is often there for miracles, usually healing; Mark doesn't tell much of what Jesus preached to a crowd outside bet-midrash. Mark knew that Jesus had teachings, and Mark respected those teachings; so it is of interest that Mark doesn't have his Jesus delivering a summary thereof to a general audience.

- unless Mark was saving it up for later. At the end he'll issue the famous chapter 13, an apocalypse. Mark prepends this sermon to the Passion chs. 14-15, in Jerusalem. Mark 13 is, for that Evangelist, that News which Jesus came to deliver. (Recall Papias/Pierius warning that Mark doesn't arrange the events in the correct sequence.)

Matthew, updating Mark, has an update to Mark 13 in his own chs. 24-5. But Matthew by contrast also offers what Jesus said to the crowds, before all that. This sermon from the mountain is entirely not Mark 13 / Matt 24-5. This (for Matthew) would be the capstone manifesto of Jesus-ism (if you will). Matthew figured Jesus for the latter-day Moses, not an Elisha or a Joel or whatever. Luke was more concerned with the Spirit itself, which can come through Jesus, but can also come upon and through the Apostles as at Pentecost - although, here Luke had other motives (which I'll get to).

One argument is that the Sermon On The [?] was a stumpspeech which he shopped around the various villages. Luke got wind of one version; Matthew of another. In effect a hellenophone stenographer of Christ Himself would be "Q".

Against this, Luke and Matthew aren't acting like tradents of "Q". I would bring the sociology of Matthew versus that of Luke. For Matthew, is a hierarchy: G-d above, Christ, then Saint Peter and finally the camp of the sainted people. Matthew's Jesus blesses the poor... in spirit. Luke's Jesus, on the same (altitudinal) level as the people, blesses the poor. Matthew's Jesus forgives sins; Luke's Jesus forgives debts. If we allow that these two speeches are in two different places, then Jesus was a first-century Yassir Arafat: preaching hierarchy to group A (in Greek?) and socialism to B (in Aramaic?).

On the one hand, yeah; these were not the same speech. But they are relayed by not-the-same tradents. I do not think so little of Christ's ethical mindset as, apparently, Christian fundamentalists think.

Matthew acts like one steeped in Torah. Luke for his part acts like he knew Matthew's Sermon on the Mount, disliked it, but had to relate something like it. (Luke will do similar with Pentecost.) Luke figured that if there existed such a nonapocalyptic speech, it must sketch the socialist Assembly as Acts will portray it.

The historian must default to Crossan's dictum. To whit, we are not here to explain(-away) what could have happened, but to figure what most-likely did happen. What happened here is that Matthew concocted a Mosaic speech, in all senses of "mosaic". Luke smelled a rat and, why not, since Matthew is doing it, why not me.

Overall Mark, once more, is the most-likely right. Jesus did have a stumpspeech. That speech was Mark 13.

MEANWHILE 9/10: POxy 5575 presents another synopsis for Matthew. The Evangelical Textual Critics, in a supreme irony, announced this whilst my poast here was in (gradual) composition. I think this relays Matthew's source (and Thomas' of course).

TOI-4600

The transiting-scope TESS is still at it. Ismael Mireles et al. have reported in on the object-of-interest 4600.

Gaia meanwhile has data on this star as well, out at parallax 4.620 ±0.011, which is sadly single-digit (216.45 parsecs). And it's a dim one, a K slightly over 2/5 our own Sun's luminosity. Age isn't well-constrained: 700-5100 My. They do think they've constrained its mass at 0.89 ±0.05 M_⊙. This wasn't done by Kepler on account there's no radial-velocity constraint on the planets.

Right: that's a plural. Two of the things are transiting the star. However much they weigh, they're big: 6.80 ±0.3 and 9.42 ±0.4 Earths. Both are Saturn-size.

Metallicity of the star is 0.16 ±0.08 Fe/H. Usually hot-Jupiters form at 0.25; our Sun's is a, er, hot topic but is typically considered 0.012 or less. One reason why the paper figured this star for a later-generation star therefore young. I would guess that at least the inner planet is high-mass with a thick gaseous envelope, not as Saturnlike as its volume suggests.

Neither of these two are in the habitable zone. The inner one 0.35ish AU gets a little more warmth than Earth and that'll be in the infrared, so its moons (if any) are venuslikes. The outer one 1.1-1.2 AU (it's only been caught transiting twice, so there's less constraint) is just plain cold. They think cold as Ceres, based on similar sources as John Cougar Mellencamp's statistics (just give us the stellar flux, guys).

Anyway the outer one could run elliptic. Again, little constraint, beyond that it shouldn't be mixing Hills with the inner one. At least we know the planets aren't resonant (29:5? lol). It could be that they were 6:1 in the past, though; that might contribute to present eccentricity.

Could there be an earth-habitable planet, in between? High metals imply that planets in the habitable zone, if they have oxygen, won't have ozone. And I'm concerned that the inner planet is a heavy-hitter with a wide Hill.

800k BC

After Dartnell's variability event between 900-800kBC was a bottleneck. Although, since no humans survived excepting the ancestors of Neanders and of us, this is a difficult call if it were a true wipeout of those other early hominids.

Our ancestors came out of a tribe of 1280 fertiles. Sharing chromosome-2, they think. These - in Africa - went to stem-1/stem-2, with the Neanders leaving Africa by the 600kBCs. Although protoNeanders may have branched off at the end of the cursed 800ks.

I vaguely remember some talk about Homo-antecessor in Europe, which was at first thought to be Erectus. And yeah: 700kBC, this coalmine, in southern Greece. These remains are considered not-Neander. How was their chromo-2? Honestly I have to suspect they are actual early Neanders.

SHIFT 4/22/25: They're now saying 928-811kBC.