"It's the start of a Journey. Not a single mission."-Jacob Bleacher

"Sustained. Whatever your definition of that is."-Sara Noble

Artemis launch has been delayed for three more days at the time of this post. Once launched, the Orion capsule will fly autonomously carrying a variety of instruments including some cubesat experiments. It will be bound for Luna, and once there it will make half an orbit or one-&-a-half orbits before returning. 

This LPI lecture came out earlier in the year. It covers the whole scope of what Artemis intends to accomplish, including construction of The Gateway. Artemis-2 will be a manned mission without a lander. Artemis-3 will attempt to land astronauts at the Lunar south pole. 

These kinds of pre-mission presentations tend to involve fewer slides, and a lot of the speaker simply reading their slides aloud, so I won't call attention to their timestamps. However, this Artemis thing is much larger than even a flagship mission like Cassini. This is literally a mandatory step in making the solar system part of our world. Not just Earth. Therefore this video is quite unique. 

A great deal of the content involves a call for the mission team. Because the scope of Artemis is huge, and because boots on The Moon don't come till Artemis-3, much of the staff, as well as Gateway parts, haven't been assembled or even identified yet. In other words if you are a geologist or engineer, you have some form of a chance to apply for a role, provided you are a member of a team that can fill that role.

The latter half is packed with information concerning what Artemis astronauts will be dealing with. You can kind of get a sense of the dramas they will be facing.

I cant stress enough how big a deal this is. We may be used to amazing probes like New Horizons, Cassini, Voyager, and the Mars Rovers, but Artemis is a prerequisite to having better probes. Probes that can be assembled out of parts that weigh as much as current probes. Probes that can fly faster, further, and get into orbit around smaller targets, even land there. 

"If you asked anybody in Mars science to come up and give a talk discussing the discoveries and insights of the past 50 years you'd get as many different perspectives as as you had scientists." -Stephan Clifford 

Note that with formal hall lectures, there will be a hype-man that will read the speakers resume before the lecture starts. This one starts at 16:45. Feel free to skip to there. 

This is probably one of , if not the first lecture someone should review on Mars. Stephan Clifford is the Mars guy. Probably one of the best Mars planetary-scientists, and certainly the best lecturer. This lecture is three years old when I post this, and the most recent of Clifford's lectures. His previous lectures are different, meaning he never gives the same lecture twice, yet all are relevant. Five years is nothing to the progress of planetary-science.

This LPI is a catch-all lecture for Mars. It is a direct answer to the question; what are planetary-scientists really doing behind the ivory-paywalls? Turns out they are shifting the view of Mars dramatically from what it was before Pathfinder.

• At 19:20 Clifford is calling attention to a slide showing the ice-cap coverage with the seasons. This, like other things, such as Mars periodically tilting, are things everyone knows and no one thinks through. It will come up thematically in this lecture. Water (& CO₂) is getting to the south Noachian highlands with each season using only sublimation and frost. Keep that in mind.
• At 28:50 he calls attention to another tongue-in-cheek detail people seem to forget. Ice is very much a mineral, and on Mars it is often part of a sedimentary strata. What happens when the ice sublimates under the surface? 
• Slide at 34:50, Clifford drops some deeper questions regarding Mars. Contrary to what is sometimes believed, large Mars river channels usually lack any kind of certain tributary (smaller feeding rivers). But what Mars does have is a Noachian source and some weird "hummocky" terrain that the bigger flows seem to emerge from. All these bullets are connected. Sublimated glaciers and groundwater layers with an episodic influx of heat seems to be a large part of what forms these channels. In the image hes talking about, an obvious moraine is present, so glacial action is also involved.
• At 41:10 it is mentioned that Mars is believed to be younger than most other worlds in the solar system. It's possible that Mars had a resurfacing event. It's also possible Mars really is younger, or that it had an orbit too close to Jupiter for too long. Both of those last two options seem to be stronger, since Mars seems to be depleted of heavy elements even for it's size.
• From 47:20 on Clifford describes the growing rift between the old way of thinking about Mars and the current way. 

Clifford always has this soft-spoken subtlety in his presentations. He chooses words carefully so not to step on toes, but he will drop a sheathed-point pretty regularly. If your experience with Mars is poor, you may miss a lot of meaning in his sentences, but one of the best presenters to upgrade your experience with Mars is him.

Here is a bonus lecture from Stephan Clifford in 2017. Similar but not the same content.

"These images were such a delight to look at." -Emily Costello

Ganymede is one of my personal favorites. Partly because it has plate-tectonic activity that might be active, more similar to Earth than any other world. However the similarities don't go far, because Earth-like subduction and buoyancy differences between granite and basalt are off the table. Ganymede uses different rules to do different things than Earth thought to be related to ice expanding as it freezes. But there is a catch. The Sulci of Ganymede seem to take up more space than water freezing alone can explain. The simplest explanation is that the Sulci didn't rift at once, they took turns.

That's what this fantastic LPI lecture is doing, dating the relative ages of the Sulci by crater-counting.

• At 6:40 the speaker starts showing craters on trailing Sulci. Leading and trailing are important terms with moons. Jupiter is attracting impactors, and Ganymede's leading end will collect more than the trailing end. Since Ganymede is tidally locked, the leading end will always be the same.
• The slide at 7:00. Look at Tiamat Sulcus. Is it older or younger than Kishar Sulcus? The one that crosses the other is younger. Which one is younger in this image? There seems to be another Sulci inside Tiamat Sulcus that is the youngest, while Kishar is younger than the rest of Tiamat. But the youngest thing is that crater right on the intersection there, and there aren't very many craters in that image. See how fun Ganymede is?
• At 9:00 the speaker demonstrates the same law-of-superposition, (younger is on top), principal, just in a mathematically absolute manner.
• At 10:10 the speaker demonstrates a conflict between eyeballing the law-of-superposition and her mathematical model. In every case, the law-of-superposition wins. The likely explanation is that where they overlap, the newest Sulci wiped out the craters on the bottom Sulci, thus skewing the numbers. 

The bottom line is that Ganymede craters do make for an accurate method to date Ganymede's Sulci, and that the Sulci vary in age considerably. But there's another funny catch to consider going forward. Europa's double-ridges are thought to be related to where Europa's crust happens to be (since it's floating) when it pulls towards or away from Jupiter. The Europa ridges tend to come in arcs this way, and periodically appear with ongoing frequency. Ganymede has very different morphology, but the root cause may be similar. However Ganymede may not be gaining new Sulci anymore if the ice-lithosphere is thick enough to resist and insulate. Ganymede has internal heat, and the thermal expansion of ice may be in equilibrium.

"Collisional models predict a lot more of these craters." -Patricio Salvador Zain

Did you know that the asteroid belt is one and a half AU (the distance between Earth and Sol) deep? And that all the big 4 asteroids including Ceres and Vesta have unique and distant orbits? There's a lot going on in the asteroid belt, but people overlook it. Not this speaker though, this LPI reveals the model all planetary scientists are now using.

• The slide at 2:00 demonstrates that the belt is divided into six parts, six separate neighborhoods, that are all in resonance, meaning the individuals will rarely collide with anything big. At least not naturally.
• At 6:10 we learn that Ceres is strangely depleted of large impact craters. That's what killed the old asteroid belt model. It's a direct discovery from the wildly successful DAWN mission.
• At 13:40 you see that Ceres is mostly impacted by objects from the outer belt, and second from Ceres' own neighborhood, the middle-belt. While Vesta the dominant asteroid/dwarf planet in the inner belt, is least impacted by it's own neighborhood, although all six belts are about the same. This has to do with asteroids still working themselves into a sustainable resonance. The ones that haven't got there are the ones most likely to impact something, and they most likely will come from closest to Mars.
• Conclusions at 16:20

Ceres and Vesta, along with Pallas and Hygiea, actually dominate their relative parts of the asteroid belt. It really is six different belts, not one. This is the tip of the iceberg though, studying the asteroid belt is a lot like studying the moons of Saturn and Jupiter. The more you look at it, the deeper it gets. 

This LPI was made because previous assumptions about the asteroid belt don't fit the observations. And you can tell from the speakers presentation, that the now updated model will still evolve with time and more observations. 

Benjamin D. Boatwright & James W. Head

"Inverted fluvial channels"-Speaker

Great news. This one has timestamps embedded already. Better news, the slides are beautiful and packed with knowledge-bombs.

In the southern Noachian Highlands where the most ancient craters have not been wiped-out by erosion, they've still been eroded a bit. The rims are low and the basins are infilled. Some have a channel leading into them with an alluvial fan, some alluvial fans don't have a channel, but essentially most Noachian craters have an inlet of some kind, and quite a few have an outlet too. Classically people have assumed rain to be the erosive element, albeit very rare rain. But you don't need rain to explain things, and with each probe regular-rain becomes less and less a possibility. 

• The slide at 5:55 has an example of lake features in a crater that has no obvious inlet. The implication is that groundwater seepage was involved since there is no inlet, but there are alluvial fans.
• At 8:50 the speaker is still building up to the overall point, but that's because it is a HUGE point. Still I wanted to call attention to slide since it displays these inverted fluvial channels so well.
• At 10:30 the speaker begins to make the argument that the crater features, were most likely formed in cold conditions. RSL's, recurring slope lineae, those are the "water-steaks" that have been noted forming and disappearing currently in the late Amazonian era. The suggestion is that the mechanics are the same.
• At 13:45 the overall question is asked. 'are the features we see explicable by episodic melting events.' And where the climate models have always said that's what has to be, the geological evidence had been lacking, until this.
• The whole lecture, including the Q&A is entertaining. Great questions come up.

These inverted fluvial channels are best explained as brine flowing under an icecap. Activity under the glaciers. That's why the cliff-facing-scarps have that backwards curve, and why the fluvial channels are inverted. You know how you see river beds on Mars and assume they are depressions instead of highlands because they look like dendritic rivers, but for some reason they usually aren't braided streams? That's because it's a cold fluid brine acting like a fluid brine, and not a river not acting like a river. 

"Some of the very largest secondaries, [typically those are usually about five percent of the diameter of the primary.]" -Kelsi Singer

This LPI is a study looking to infer what happened in the impact process. It's looking at secondary craters, craters made from the largest debris from the initial impact. So the size of debris should tell you something. What exactly?

• The slide at 3:20 really gives you a feel for how many craters can be secondary impacts, not direct foreign impacts. This can be really eye-opening. The smaller debris are more likely to make escape velocity than the larger ones.
• At 4:20, a high resolution close-up of diminutive secondary craters.
• Slide at 4:32 shows you the V-shaped features, implying debris was skipping! Or at least entering at a very low angle.
• Faint V-shaped secondary close-up at 5:00.

The remainder of the lecture is a whole lot of isolating simple variables to make estimation of ejecta more formulaic. This isn't difficult algebra, but it makes it plausible to do stuff like find an asteroid with a certain mass and velocity, and maybe scale back the path it took eons ago, to its initial crater. Albeit that wont apply to most asteroids, but that's sort of the upper-limit of what this kind of research can do.  

 -Ashley M. Palumbo

"Abundant erosion that cannot be fully attributed to background erosive activity."

This LPI is a bit of an oddity in that the speaker isn't the speaker, they are the slideshow producer.

It's a simple concept. A massive impact has massive effects, right? Well on Mars, we expect that to be doubly true, since even small impacts seem to have had profound effects. 

Argyre Basin is the third largest Noachian impact basin after Helles Basin and Isidis Basin. They both represent the end of the Late Heavy Bombardment and the middle of the Noachian era. That basically means that the dynamo is long gone, the majority of peak-atmosphere is long gone, the big shield-volcanoes are just getting started, and Valles Marineris is an era and a half away from starting. Most likely topical-Mars is very frozen and still, just with a lot more ice than Amazonian Mars.

• Pay attention to the slide at 3:40 and how not-still such an impact potentially can make Mars for a few centuries.
• At 8:00 there is a nice slide comparing a similar crater on Luna, which has essentially no weather, and Argyre which experienced weak weather. Part of the argument in this lecture is that the weather caused by the Argyre impact is what eroded the older craters. 
• At 12:10 the speaker mentions something exciting that Percy can do to test these premises. It will be a few years, but Percy has the chance to sample Noachian Mars, no lander has to date.

Among the great and persistent misconceptions that are ubiquitous in the click-bait media is the premise that Mars has an Earth-like lithosphere. It doesn't. Mars surface as anyone who has seen Percy or Curiosity drill into, is very fragile and porous. Yet the weather is weak, so much so that the soft ground once altered, stays altered. Over the eons, any great event, stays in the record.

This is why all major Mars formations, including riverbeds, eskers, and glaciation, are best explained as episodic. This LPI lecture, performed at the same conference as this one, may help some understand better. 

"I haven't really answered any questions yet." -Michelle Kirchoff

This is a really fun LPI. It involves comparing images of craters with focus on Mars' presumed wet splat-type rampart-craters.

Here's the thing, the law of superposition works well with crater ejecta. However you can't really interpret more than a few layers of overlapping ejecta. It works best on places like Callisto and Ganymede but also applies to Luna, Mercury, and Mars.

Mars in particular gets weird because it has a lot of Rampart-craters. You can employ the law of superposition in the Noachian south, but not so much around the Hesperian equator. So how do you infer some relative dating?

• Slide at 2:60 shows a random distribution for both Ballistic-craters and Rampart-craters on Mars.
• From 10:00 on she's showing older images compared with newer images of the same craters to demonstrate how the interpretation of ejecta type has changed. 

One would think you could just say that Rampart-craters are older than Ballistic-craters, but that doesn't seem to work. Frequently craters have traits of both types. It's entirely possible that all Rampart-craters were hybridized at first. Wind erosion seems to have dulled or removed a lot of radial ejecta.

In the end this LPI is the type that brings into question things one would have thought fairly straight forward. Which is neat. Now one can say that currently, in the case of Mars, dating craters is a bit more complicated. And this further throws into question the chemistry/mechanical-action that causes Rampart-crater morphology.     

"People assume a bar, I think, largely because that's what we have on the Earth" - James W. Head

So there's a huge detach between the idea of blue-Mars and real-Mars. You see, the south hemisphere exists. 

The southern Noachian highlands are dated by crater counting to make the surface at least 4.1 - 3.7 billion years old. There are magnetic bits in the Noachian south, but they are not heterogeneous. They are not oriented in a particular direction, implying that the lithosphere was still somewhat plastic when they were made, and they seem to have been destroyed by giant impactors, and are not present in or around the largest southern craters. Taken together this implies that when Mars had a magnetosphere, was also when the crust was still semi-molten, at least 4.1 billion years ago. 

This LPI is searching for answers. Mostly, it's identifying the questions. What does this mean about Mars atmosphere at that time and later? After-all, the craters have not been eroded... much. 

• I like the slide at 7:30 just for giving us a nice guideline. Multi-ringed craters are probably older.
• At 13:00 a slide showing sort of the old model, or the model that is under interrogation in planetary science. 
• The slide at 13:50 I just want to mention for my own reference. That beautiful map showing the headwaters for Jezero crater is one I think I may refer to in the future.
• Slide at 15:50 is where the problems kick in. If Mars had precipitation at all, it wasn't much, but the Noachian highlands still need an explanation for how much water they did cycle. This continues to be an unresolved and hotly debated topic. 
• So now you see the debate. The slide at 16:20 and the slide at 15:00, are showing incompatible modeling. The data supporting one model conflicts with the other, and they must be resolved to find real-Mars. 
• Slide at 17:30 details the ongoing questions to answer. Q2 will be very hard to answer, questions 3 & 6 seem more likely to get answers in the next few years. 

So this lecture wraps up a topic that I promise you, planetary scientists are almost willing to kill each other over right now. There's a lot at stake. Blue-Mars has no harborage in the Hesperian anymore, and may not have room in the Noachian either.

"They didn't look like any concretions I'd ever seen" -Donald M. Burt

Alright, so this LPI is literally elementary for understanding Real-Mars. Almost everything in it is fundamental yet no one outside the planetary science field will know any of it unless they really try, and actually watch this LPI. Almost every spoken word in this LPI is golden. 

• The facts come hard and fast in this LPI. Slide at 0:30.
• Slide at 2:57. Dust can explain most Mars deposition. It wasn't water, it was dust that put the most common layers down.
• Pay attention to what he says at the slide at 5:40
• Super important. The slide at 7:11. Listen to what is said, and then note the importance of the new rover Perseverance which had not yet landed when this LPI first was uploaded. The Kodiak mesa has cross-bedding inside it. It's a huge deal, and planetary scientists are keeping it on the DL for now.
• At 10:00. The theory about blueberries is now changed forever.
• At 10:30. The Cross-bedding dilemma is explained perfectly.
• Slide at 13:40. The plains around alluvial fans have more material in them than the canyon cut volume can fill. But the canyons funnel impact flows, making up the lions share of the deposition.
• Slide at 15:30, simply drills home the Blueberry dilemma.
• Watch the questions too after 18:30.

You rarely get knowledge-bombs dropped with this kind of frequency. LPI's and scientific papers are usually focused on one detail. This LPI represents one of those moments in history where a common belief is blown away by pure logos. 

I'll tell you the endgame of this. What all the Mars science is heading to is that Mars has always been an ice-ball losing it's ice. Glacial action dominated the north through the Hesperian, but only episodic action, eruptions and impacts, cut the river beds and gullies. It possibly never rained outside impacts. Mars lost it's magnetosphere and the lions share of it's atmosphere at the same time in the Prenoachian,when the crust was still mostly soft. There never was a "blue-Mars."

"I'm not necessarily here to advocate for Neptune over Uranus but..." -Abigail Rymer

This LPI is about a misson proposal. A flagship budget to Neptune. Strictly speaking, it's less likely than a similar Uranus mission because Uranus will be in a better position for the next decade; they move slow and wide. 

This begs the topic though, so much of the outer solar system is so far and inaccessible, yet so baited with temptations, that I wonder if it will compel engineering in the near future. This, the age of probes, and so many targets are so far and separated that scientists are discouraged before they try. Wouldn't it be nice if we could get the probes to go faster, and still get into orbit around objects with scant gravity? Maybe two delta-V launches, the probe, then a bonus fuel tank for the probe. It's sad to realize many of these temptations cannot be reached in my lifetime, and I would like to be greedy.  

This short mission proposal LPI actually has it’s own time-stamps between slides. It's intuitive and needs little paraphrasing from me. Probes themselves begin to have personality at some point, and this is one I would like to meet one day.   

 -Sean O'Hara

Cryovolcanos are peculiar. If not for Triton I wonder if people would find the topic so interesting. However... Triton. Among the most active worlds in the solar system, and so far away a return mission isn't forthcoming. 

• The slides in this LPI are self explanatory, so I don't feel like I need to call attention to some choice timestamps, but at 12:00 the future of planetary science makes an appearance.

There are 5 cryovolcano suspects named.

1. Ahuna Mons on Ceres at 11:00
2. At 13:30, Hubble says there might be plumes on Europa, nothing confirmed. 
3. At 15:40, Enceladus' Tiger Stripes, the most studied Cryovolcano of them all. 
4. Triton at 17:20. With a mission teaser. 
5. Pluto’s Wright & Piccard Mons at 19:00. Not confirmed at all, but odd enough to take a hard look at. 

At 28:40 in the Q&A he shows you some of the "anti-freeze" chemistry in videos. Lab-lava in it’s cryogenic form. At 34:00 he models a volcano with chocolate. It’s even better than I’m making it sound.

If interested in more check out Fire & Ice by Natalie Starkey.

"It's just jargon to keep people out of the field." -Lindy Elkins-Tanton

So this LPI is a great teaser for the Psyche mission to Psyche. I think I've seen this speaker give more-or-less the same slideshow as an LPI 2-3 years ago, but it's a great presentation that isn't so high-brow that I need to paraphrase it for a more general audience. Some of the slides are straight eye candy, all of them are intuitive. 

• At 18:20 a Vestoid (by far most asteroids are vestoids) compared to a classic M-class
• The very next slide is something beautiful combining the interesting traits of both
• Most of the slides after 25:00 are mission planning and goals

Psyche was supposed to launch this year, about the time of this post. It was delayed for software problems. The next launch window will be next summer, July and August. It's physically located at Kennedy until then.

One thing to note is that Psyche will be carrying a very powerful magnetometer, and will (probably) do a Mars flyby. Mars missions usually don't carry magnetometers for a variety of reasons, but Mars density is a constant topic, so it may be fun if a measurement gets taken. It has another instrument, DSOC, which is Mars related and described around 30:00.

Watch this LPI if you want to learn much more about M-class asteroids.

 

There's only one thing I grade non-fiction on. Does it teach?

This does. It doesn't teach the most accurate information. It's sensationalist; starting-facts exaggerated enough to cross the line into 'wrong' sometimes. However because the author is not an expert, that not only works, but may in fact be the correct thing for a modern & moral person to do in this day & age. 

At its core, this book is an ammo-can. It may not appeal to a group outside an echo-box, but it excels at arming those in that group for some family debates.

 

 Soft robotics are key to wearable tech, things like Jovian wet-suits in Sweet, and also humanoid androids such as followers. This Science Daily article describes a problem and breakthrough along that line. 

"the research introduced the innovative concept of bifunctional polymer. By forming a one-dimensional ion channel several nanometers wide inside the polymer matrix, which is hard as glass, a superionic polymer electrolyte with both high ionic conductivity and mechanical strength was achieved."

"What's interesting about these organisms is that they are very sensitive to environmental changes" -Jahnavi Punekar

This LPI is about mass extinctions. Big die-offs like the one Humanity is currently causing. It focuses on dating and analyzing using foraminifera, or forams for short. These like diatoms, leave hard shells when they die, but they are single celled. That means they evolve rapidly, and the shells are diverse. It's easy, real easy, to chronologically date ocean sediments this way. Takes a lot of the guesswork out, no need for radiometric dating. 

Of course, forams are very sensitive to environmental changes, so guess what's happening to them right now?

• At 17:40 she actually shows you the specific foraminifera that were-then-gone at the KT extinction. 
• At 20:20, the term "disaster opportunist" gets used. And the implications are interesting. 
• 24:50 Mesotrophy opportunist blooms. Have you heard of dead-zones in relation to river outlets? 
• At 42:00 the conclusions. One theme in here is a greater emphasis on the Deccan Traps being involved alongside the Chicxulub impact at the KT boundary. She demonstrates the case well. 

In general I want to credit this speaker for her use of assets. Her slideshow skills are a notch above average. In other words this is a very colorful and intuitive LPI. You don't have to be an ultra-nerd to follow.

"Some of the largest of these impact events would have blasted fragments of the Earth's crust up onto the Lunar surface" -David A. Kring

A major theme in this LPI seems to be an origin of life hypothesis involving hydrothermal systems that are caused by impact craters. As it turns out, Dragonfly is going to try and feed data into this hypothesis at Titan. Curiosity has and is working under the notion that the heat that powered the waterworks of Gale crater came solely from the impact that made Gale crater, not Mars-climate or the influence of The Sun. So this impact-local-hydrosphere is thematically a thing planetary scientists are picking at.

In relation to Earth, Hadean Earth is pretty inaccessible, except when talking about Luna. Lunar craters date to the Hadean era, and there may be some impact basin hydrological exchanges there. Can't say, but don't ever think that future Lunar missions will have a low science return.

There is of course the odd chance that a Lunar rock can be found that is ejecta from the Chicxulub impact, or a Hadean impact. No doubt the samples are up there somewhere. The question is if or not they can be found. 

• You've heard of shock-quartz. At 7:20 an image will burn into your memory what it looks like.
• At 12:10 you get a comparison crater. A lunar crater that is about the same size as Chicxulub.
• In truth most slides are eye candy, so I don't want to list them all. Tons of mineral close-ups and thin-slices.
• At 27:00 you get a sense of hydrology under an impact basin.
• Conclusions at 46:00

"The Moon preserves the early history of the Earth-Moon system" -Carolyn Van Der Bogert

Geological time. Crater counting and whatnot. Anyone who says they understand it intuitively, is lying. You have to let the scale sink in, and then bunches of things you don't know start assaulting your insecurities. This LPI can help. 

One funny thing that lurks in the back of my mind is that if you google 'how old is the surface of the moon', it spits out 4.51 billion. If you change that to Callisto... 4 billion. The odds are great that Callisto is way way older than Luna. Jupiter formed first, Luna formed well after Earth was formed, resurfacing Earth and Theia. That was long after Callisto should have been a thing. Of course the rules are different for each world, but when you go down the list, how old is the surface of Mercury, Iapetus, Hyperion, Ceres, Vesta, even Ganymede, you keep getting 4 billionish. Hell, even Noachian Mars comes to 3.7 (aka first life on Earth) to 4 billion. A billion is a lot, but it's hard to imagine Luna's surface is as old or older than Callisto's, Mercury's surface is extremely-likely much younger than Mercury, so the dating that is being used is clearly inexact. 

And this LPI teaches you all you need to know about exacting. 

• The slide at 7:20 is a pretty on-the-nose guide to the rules of relative dating via crater counting. 
• A very statistical comparison of Luna and Mars comes at 18:40
• At 20:30, somewhat unrelated but I wish I had a URL for the slide/image she keeps referring to. A painting one student did for her. 
• The slide at 25:50 is a geological map of the Apollo 12 site. 
• At 47:30, another great geoplogical map, this time of Aitkin-Basin.
• At 51:30 a marvelous slide comparing of Earth, Luna, Venus, Mercury, and Mars time. Huge payoff. 

This LPI is pretty pointed for an audience composed only of established planetary scientists. So I'll add a shorter LPI that is slightly less so. The two don't overlap much, but combined any dedicated person should understand crater dating much better. 

This one presented by Alexandra E. Huff. 
  

 -Rachel L. Klima

This is a really easy LPI to love. The slides are lovely and intuitive, partly because Europa scientists have had tons of time to salivate and trade graphics.

If you were an alien looking from a distance at this solar system, you could be forgiven for thinking Europa was the most likely place to find life. Mars life is just talk, Venus, Titan, Triton, Enceladus, sure maybe; but there really actually might be something going on inside Europa. The difference is huge because Europa has been going like this since longer than Earth has had a solid surface.

So why not fly a lander with a drill instead of Clipper? Because you don't know where to land, and how much of what kind of drill to bring. The range of what the crust thickness can be has kilometres of error involved. Europa Clippers primary mission is to find a good spot, which happens to involve collecting a ton of science anyway. 

This LPI is a very excited preview. The closer the mission gets the more enthused the scientists get. You can really feel it. Like they're planning their haul before they go trick-or-treating.  

• That slide at 10 is gif worthy by itself. Showing the IO flux tube aside Europa's induced magnetic field.
• At 16:30 the concept of "subsumptions". Basically a forced rifting in sort of a slip-strike sort of way. But that's awesome, because it's not a common thing on Earth, but may be a regular thing everywhere else.

 The sedimentary rock record is significantly older than what we see on Earth -Michael Thorpe

This LPI is about Curiosity in Gale crater, not Percy in Jezero crater. However, they are both Hesperian environments. Gale was picked to be a slam-dunk sure-thing, late-era yet wet spot; Jezero is supposed to have more sedimentary action going on, and so far does.

Most of these slides are not so high-brow that someone only loosely familiar with the terminology would struggle to follow, but the first half of the LPI is building an argument. So if the early slides seem confusing, skip ahead, you aren't missing much.

What's happening is that clays tell you a lot. Clays tell you about weather, and wetness. The speaker is seeing where clays had time to form, and where they did not. And the contrast is telling. Mars is naturally porous, clays are denser and take time to make. So, among other things, you can measure how long, and how much of a part of Mars was "habitable" by observing clay deposits.

• I like this slide at 5:30 so I just want to mark it. Any time I can reference a good time-scale helps me personally.
• The slide at 22:50 really brings the LPI together. All the slides after are thematically in line as it is a very well constructed argument the speaker is making.
• Final thoughts at 40:00

The story of Gale crater is:

1. There was a Hesperian patch of Mars.
2. A crater-maker hit it.
3. The crater was now hot.
4. Some water flowed into it, cutting a short and deep canyon.
5. Ice-cap over that water, and some groundwater flows.
6. The water makes water-minerals.
7. The water leaves.
8. The water-minerals dry out.
9. Wind goes over the crater rim, picks water-mineral dust up from one side, and makes a mountain of it on the other.
10. The dust hardens into Mt Sharpe.
11. Curiosity goes to look at it.
12. It's still a crater that whole time.

So the fact is that Gale crater was never a good candidate to find "life", but it was highly likely to benchmark climate chemistry. And it did, this speaker is actively doing exactly that. The volumes and compounds of clay in this closed environment is now a usable measuring stick to compare against less controlled environments. Like Jezero. 

We're driving over around Mars, and we're looking at all these sort of inorganic rock minerals,searching for any organic molecules that may be trapped inside them. Whereas on Titan, organics are everywhere -Melissa Trainer 

This LPI is more science and less engineering than the last one I put up. Which because the Cassini mission was so crazy good, and a little time has past, means this LPI is packed with good slides. 

Complex chemistry. If I tried to rank the complexity of atmospheres, Titan, Earth, and Venus, I couldn't because Venus hasn't been studied enough, but Titan has, and is more complex than Earth. This is a big part of why Titan is irresistible. It's un-Earth-like traits and Earthlike traits combine to make it attractive and scientifically usable. 

• Slides kick off early at 9:00. Pretty must every slide is lovely and informative.
• At 18:00 there is a simple slide, but it makes me think. Titan is the only world that rains to a surface aside Earth. It has winds comparable to Earth. Yet some worlds like Triton and Europa are cratered about as much.  
• Slide at 25:40 she repeats the bit about wanting to see what happens when an impact packs hot organics into Titans surface. I'm hearing that bit repeated a lot from the Dragonfly science team so we can take a flagrant-hint about where Dragonfly will be looking to go. At 33:20, the name of the crater is 'Selk'. 
• At 35:10 and after, Dragonfly's planned route is made explicit. 

In general, the extraterrestrial search for life does not inspire me much. I find it overplayed, but then when it comes to Europa and Titan, I can't help myself. Europa is almost more likely than Earth if you didn't know better. And Titan, far less likely, but there is so much possibility. 

One thing that sits in the back of my mind regarding Titan is the idea of a benthic environment. No doubt silt of Titan is different and follows different rules than Earth. With life, water sorts polar molecules and separates polar from non-polar, so you already have a basic organizing to start with. On Titan the seas are non-polar, not at all like water. But the dirt is polar. So the benthic layer, where nonpolar liquid emulsifies polar particles, is a place where some sort of basic sorting can occur.

I've never heard a proper planetary scientist talk about benthic Titan. Not the seas nor the soggy flood-plains. I hope to one day, but if it's going to happen in my lifetime, it will probably be the Dragonfly mission.     

 If I don't give this five stars, then I cannot claim to know what I'm saving the fifth star for. 

The two differences between a good climate change book and an average climate change book are simple; do they address carrying capacity, and do they have some solutions in mind? This one does, and does so elegantly. The solutions are a tad debatable, and that is the only flaw I can find. 

You can hear the authors narration as you read. The book is well paced and does not dwell on the already overexposed symptoms, but calls out the root cause and makes suggestions. It teaches each point well. There is nothing for me to do but recommend.

 This is the most depressing non-fiction I've ever read. Not only does the author somehow manage to die at the end (tholins are carcinogenic), but all throughout he is clearly, simply, and pointedly, laying out all the ecological and economical problems we are currently failing to deal with. He died in '96. Worst death letter ever, only read if you want to mainline shame.