"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.