@mcaplinger

Without attempting to debate the definition of a planet... given some reasonable assumptions about composition, and what is known of Hygia's density and mass, surely this can be quickly settled by calculation, at least to a reasonable approximation?

A paper in Science raises two intriguing ideas. The first is scientific: The hydrocarbon dunes may be 'grown' from hydrocarbon ices undergoing a yet-to-be-fully-pinned-down reaction powered by cosmic rays. That could also explain their presence on airless solar system bodies. Paper here

The second is... artistic: According to Michael Malaska, who studies planetary ices at NASA's Jet Propulsion Laboratory in California. "Their work further supports that some of Titan's sand may glow pretty colors under UV light," That was reported in a Space.com article, here: Bring a powerful blacklight to a dust storm on Titan and your might get some mind-blowing visuals.

There is the possibility that we may get to see the LRO images before we do the Chandrayaan 2 ones! ISRO, love you, but I've been spoiled by the relative hosepipe of data and images NASA prefers, as opposed to the more cautious approach.

The word from The Times of India is that Vikram is on the Lunar soil in one piece, but tilted on its side and possibly (probably imho) damaged after a hard landing. Even if it's functional there's a good chance the angle it's at will prevent communication, but the ISRO team will keep trying for the rest of the lunar day. Still, it looks like this was a hard but controlled landing, not a crash, and I think it's safe to say that Vikram fought right to the end. The ISRO team can be proud of their work, and the design is clearly up to the job - once whatever bug caused the hard landing is located and ironed out

https://m.timesofindia.com/india/isro-not-l...ow/71045854.cms

Edit:: India Today's report is that the lander is not confirmed as 'intact', although I wonder if some ambiguity of translation isn't creeping in here: "In one piece" could mean one pile of bits all in one spot, or one very oblate piece. It'd be tempting to translate that as 'intact' but optimistic... Still, my statements on the ISRO team stands, even if it turn s out to be one big metal pancake.

https://www.indiatoday.in/science/story/cha...7265-2019-09-09

If this is accurate... https://mobile.twitter.com/ANI/status/1170610654232731648
... then the lander may be more-or-less intact, depending on the image resolution. A bad landing, as opposed to a crash, perhaps. That might be of some comfort to the ISRO team ifso.

In English 'gel' is something that is mostly liquid by weight, but behaves much like a solid due to a scaffold of long molecules runningthrough it... My memory of that definition may be off but my point it is that in English that word refers to a specific state of matter. Is it possible that, in Chinese, the word or phrase is more nubulously defined, or more descriptive of appearance than material state? I can imagine impact glass looks my gel like. I could also imagine a 'glass gel' of an impure glassy (by which I just mean non crystalline) material mixed with crystalline materials that might qualify as 'gel like' in another language, or specific context.

I've just started teacher training (physics), and part of it is to teach general science - so we have to get some training in biology. We just did the segment on using microscopes to examine algae and protozoa - we found a tardigrade in our sample. Looking at it it's hard to imagine it's relative made that journey (dead or alive). Not really relevant, but it was very cool and gives me a cool connection to show students how different fields of science can be connected.

This is soooo not my area of expertise, but a wee bit of googleing suggests that the lunar regolith has impressive insulating properties, and within half a meter of the surface the temperature is fairly constant at roughly -130 deg C to -150 deg c (eg, here: https://www.sciencedirect.com/science/artic...94576514004160) even at noon and midnight. Given that something hitting at approx 1km/sec will either smash to bits if it hits stone, or deeply bury if it hits deep, more yielding, regolith (and the lunar surface has little that isn't one or t' other)…. I'd (very tentatively) suggest that the much worshipped tardigrades are either slam dunk dead or in a situation where the effects of low temperature and radiation dmage accumulation on their survival are more likely relevant than the effects of high temperature.

It's not my field so I cannot vouch for it, but from what was said by this source.... https://amp.businessinsider.com/tardigrades...alive-2019-89-8
"Tardigrades in dry state can survive pressures up to 74,000 times the pressure we experience at sea level, so the [crash] impact should not be a problem for them," evolutionary zoologist Roberto Guidetti told Business Insider.

As for the vehicle... the retro reflector experiment, a small simple chunk of solid material, is thought to have perhaps survived. So I imagine that other components that are also small and basically solid chunks of material, could have survived. So not the vehicle, but identifiable components of it, perhaps, based on my layman reading of what is being said by engineers on the subject.

Ok, hang on: The tardigrades are.in their 'safed' hibernating state, and are not exposed to the lunar environmen, but sealed in layers of epoxy resin, sandwiched between layers of nickel, in an object about the size of a coin. The object is itself expected to have survived impact mostly intact. That bodes much better for their odds of long term survival and eventual recovery: A Wired article on the subject https://www.wired.com/story/a-crashed-israe...s-on-the-moon/:

I can increase the reporyed range of temperature tolerance too, down to pretty much absolute zero, according to this bbc report: http://www.bbc.co.uk/earth/story/20150313-...nimals-on-earth

Interestingly, in this state, tardigrafes do metabolise albeit at 0.01% their normal rate, and so might be argued to be 'alive' on the lunar surface. But I will say that, if I had to find an extant living thing on the lunar surface today, my 'least hugely unlikely' choice would still be to look in the mini greenhouse on the Chang'e 4 lander, assuming it still has pressure - I would bet some extremophile capable of handling the temperature swings (which would be somewhat moderated by the measures taken to keep the lander functioning) might have snuck in and be surviving off the remains of the dead plants. Ok, sorry for the lurch off topic, I'll leave it thete as a faintly amusing thought.

From what I read they can, in their hibernated ptotective state, survive lows of - 200 celcius and highs of +145. It's not clear if they were in that state during the crash, or how their tolerance holds up under the assault of the combined factors of the lunar surface. Even in the best case for them, they might stay viable for a while in some buried-by-the-impact nook with lower than average (for that lattitude) temperature swings and some shelter from other factors, but eventually the lunar conditions will get them, as the cannot leave their protective state without dying. I got the temperature tolerance infofrom here' https://www.livescience.com/57985-tardigrade-facts.html. Are webutting up against rule 1.3 here?

I just found this breakdown of the SAM lab, and including the GCMS. Good lord, she's a monster - six columns on the GC. I hated swapping columns on a single column system, this would drive me insane... Not that the columns can be changed on Mars, so I guess that makes sense since on Earth we could just swap the columns out to tackle different sample types. The article really hammers home that the GCMS is part of a battery of interconnected chemical analysis systems in SAM. I suspect that anything SAM as a whole truly cannot identify on its own will be real 'sit up and pay attention' stuff

Exactly. Unless I'm very much mistaken there will be a carbon copy of the rover's GCMS sitting in a NASA lab here on Earth, and one of its duties will be exactly that. Replicating a new fingerprint(s) may be a bit of an art, but they will have a good idea of what kinds of materials they need to start with in the Martian environment.

As an aside: I am very interested to see how this system flies when we get to environments with lots of very complex unknown organics, formed under hard to replicate conditions, such as Titan! I suspect they will already be building a database using reactions that can take place at cryogenic temperatures but that, as they say, is a different story.

Ahem. If I might pedant.... many moons ago I used to build GCMS. So, for the uninitiated (feel free to skip this first paragraph if you already know how GCMS work): The Gas Chromatograph stage works by flash heating the sample and seeing how long the components of the vapour take to travel down a long, thin, column (more like a rolled capillary tube, usually) with one of a range of coatings on it's inner surface that slow the different vapour components down by differing amounts. The GC gives you a rough idea of what is in the sample based on how long different pulses of vapour components take to hit the detector at the end of the column. In the GCMS the Mass Spectrometer is the detector. This takes the material in the pulses exiting the GC stage, ionises it (aiming to average 1 charge per molecule), and separates the molecules in it according to their charge to mass ratio. So, crudely speaking, you get a rough idea from the GC, then a more detailed analysis from the MS.

OK, here's why I'm pedanting at you all: The important point for large molecules is that when you ionise them they almost always break apart - and for a given type of ionisation method most large molecules break apart in a predictable, repeatable, fashion. So you don't get a big signal at the charge to mass ratio for the parent molecule, you get a 'fingerprint' of smaller peaks that is unique to a given high mass molecule. For example, even something fairly light weight like the amino acid glycine (mass 75 AMU) yields a fingerprint like the one I've attached when ionised by electron bombardment (see attached file). Notice that the biggest peak isn't at 75 AMU, but at 30.

So the MS isn't simply analysing heavy molecules by their charge / mass ratio - in fact that almost certainly wouldn't work. It's using these heavy molecule specific fingerprints. It can be very, very, specific as long as the molecule is known or modelled in how it breaks down under ionisation. When combined with the GC stage, and a database of known GC and MS 'fingerprints' this can be a very precise process for identifying heavy molecules.

It can go wrong : Getting the right rate of GC heating, GC column type, ionisation process and mass to charge ratio analyser stage all needs some idea to start with of what type of thing you'll be analyzing. But in this case the team behind the GCMS on the rover will have had that from previous missions.

Now, that's probably clear as mud. And, if my old boss is here he will probably now tear me apart for that explanation anyway... go ahead Vic, I'm sure I deserve it.

Life, as they say, finds a way.... but IMHO it's not likely on the Martian surface thanks to the sterilising action of the UV content of the Martian sunlight. And you'd need water to be present on or near the rover: It's not totally impossible across the whole range of Martian conditions for small amounts of liquid h2o to exist, but unlikely. Unless anyone can think of a way in which the presence of the rover might generate more favourable conditions for the formation of small amounts of liquid water, or act as such a favourable environment itself, I would comfortably dismiss the idea on those grounds alone, cool though it would be to colonisation fans.

Well done to them - as I understand it this was far more a mission about promoting STEM education, PR, and inspiring people than it was about science. They've achieved 99% of what they hoped for just by making it into lunar orbit, so well done - even a hard lunar landing is a huge achievement.

That said, I'm seriously hoping that 'inspiring people' part means we can look forward to some new (hopefully not 150 meters/sec) private landing attempts in the not too distant future......

Fifteen years on Mars. Sleep well, for now- one day there will be the rumble of wheels, or even the tramp of boots, coming to honour the robot, and the team that worked on her, whose mission was once given at 90 days...

I usually read with fascination but don't contribute for fear of denting the signal to noise ratio. However, it seems worth noting that my very un-expert brain immediately drew a connection between the weird shape of Ultima Thule and the weird shape of Omuamua. A flat, sail like, shape has been put forwards as an explanation for Omuamua's light curve I believe, and now it seems we have proof that nature can indeed craft such a flattened shape. Is it rediculous to suggest that the interstellar object could have formed in the same region of it's original solar system that Ultima Thule occupies in ours, and the two formed along approximately parallel lines under similar forces - acting in a bizarrely
pro pancake shape fashion?

I did some very crude calculations in bed last night and got numbers from 5% - 1%, but that was just working out how much KE the nano probe would be gaining per second given it's acceleration under kind of forces mentioned in the literature, and comparing that to the joules/second output of the power source. I had actually expected it to be much less, though I'm not really sure why. It is probably far too simplistic approach, and I wasn't going to share it, but it provides a bit of context for your numbers so here it is.

OK, bracing myself to eat my words, and just so I'm sure we're on the same page here: Photon momentum, individually or as a flux, is related to energy by: momentumn = Energy / c . That seems to suggest that getting the momentum of the beam from it's output energy should be (in principle, i realise there are probably real world complications) simple enough. So are you asking about the efficiency of momentum transfer from the photon flux to the sail - which would depend how close to a perfect mirror the sail is, and hence how close to all photon collisions with the sail being perfectly elastic you come? Or have I totally got the wrong end of the stick here?

My understanding is that the physics is sound and well understood, except perhaps on the matter of the antenna, which I've not done much reading on. The engineering requirements, however, are.... no cause for optimism.I've heard plausible rebuttles to most objections to the physics, again except on the transmission of data to Earth. But, again, the engineering objections are significant. Still, that's the point of the initiative: To research the issues and determine how far away we are - at least to my understanding. I've not heard anyone seriously suggesting we'll get a star-probe from this. It's laying the foundations of the foundations.

I knew it!!!

I'm going to assume that's well informed speculation and deduction, rather than you having a blue police box parked in the corner of your garage 😁 My poor sense of humor aside (sorry man, you just give such a strong sense of witnessing the history of Ryugu) , such a violent history strike me as consistent with the apparent lack of hydration in the surface material, which surprised JAXA (I guess that's part of your reasoning? ) . But given such a well mixed object, might there not still be hope of finding comparatively unaltered material?

IIRC the basis of the water detection is a feature at about 3 microns - a feature that can be notoriously hard to diagnose correctly. But I've also read that Ryugu is a g type (or cg type depending on classification system) which, again only from my imperfect memory, do not always have that 3 micron feature anyway?

True, but in fairness the investigators do mention that and other possible intepretations in the original work, and state only that, given the currently available evidence, a liquid water layer is their favoured explanation - they don't claim this is 'case proved', merely 'evidence in support of'. There's no question that this needs a lot more exploration, and the putative 'lake' is just one (provocative!) explanation at this point. Non-expert journalism, and a need to get clicks on headlines so money is made. wages are paid, and food is bought, has a lot to answer for. That said, even Emily Lakdewalla on the Planetary Society (who is usually quite groundingly skeptical) seems guardedly optimistic that this might really be liquid martian H2O. I think part of the reason is that basal melt on Mars has been predicted for a while.