Molecules with MW > 200 Found in Enceladus Vapor

That's bigger than all amino acids and nucleobases. (Note, 9 months old, I had missed this before.) Press release here, paper here. (Postberg et al, Nature. 2018 Jun; 558(7711): 564–568.)

More on the C. elegans that Survived Re-Entry During the Columbia Disaster

Living roundworms made it intact to the ground after the Columbia crash, as noted multiple times before (here and here.) There is more information in the article about their level of protection: "'They sustained some heat damage to exteriors, but that's about it,' Szewczyk said. The thermos-size metal container holding the nematodes was housed inside the locker of a crew compartment that was reinforced specifically to protect the materials inside. Once that compartment ruptured, however, the nematodes still survived the crash to Earth thanks to the locker's build, Szewczyk said. The C. elegans stayed alive upon impact because by the time that part of the shuttle fell to the ground, it had already decreased in speed, allowing the nematodes to touch down more gently." A locker is much less protection than being deep inside a solid chunk of rock.

This has obvious implications: "'From an astrobiology standpoint, the important thing was that if you had a multicellular organism going through the atmosphere you can have interplanetary transfer of life by natural means, and Columbia demonstrated that,' Szewczyk said. 'It was a fortunate thing to demonstrate that in the unfortunate circumstances that there were.'" Their descendants are kept at the University of Minnesota.

Deoxyribose From Abiotic Space Conditions

Another biomolecule, the pentose sugar that serves as the backbone of DNA, quickly produced in un-directed synthesis under conditions that obtain on ice in space. Given the speed with which the first life formed on Earth (0.1 GA after the planet cooled to a solid form) as well as increasing evidence like this about how easy it is to make nucleic acid building blocks under prebiotic conditions, it's also very likely that life forms everywhere with water and carbon - even in ice. (See here for most recent panspermia/evolution post.)

Interstellar and Intergalactic Panspermia

Active colonization time estimates for the galaxy are invariably much shorter than the lifespan of the galaxy. Passive diffusion would take longer of course but empirically observed Oort cloud mixing intervals even this far from the core for the sun are on the order of 10^5 years. Lingam and Loeb (2018) calculate the delivery of amino acids between star systems but not timescales; still, they estimate an upper bound for the size of interstellar objects for our system (a 10 kilometer-radius asteroid) and Alpha Centauri (an Earth sized planet.) This is a second source pointing to the fact that we may be an interstellar backwater, uniquely un-exposed to evidence of replicators* relative to the stars around us.

Where intergalactic material transfer is concerned, of course given the distances involved we should expect the process to be slower, both in terms of at an absolute rate and moreso in terms of colonizing systems, since the ratio of number of incoming objects:number of systems to receive material will be quite low. That said, a) there are extragalactic stars in the Milky Way right now, and b) we're actually talking about an exponential rather than linear rate if there are replicators* of any sort being introduced. This excludes infrequent but massive events like intergalactic collisions, like those which the Milky Way has undergone repeatedly in the past.

*I deliberately use the term replicators as a catch-all to include "space-viroids" (most likely), von Neumann probes, "cancerous" (mutants selected for fecundity over original function) or otherwise, or deliberate colonizations by agents with some kind of intention (least likely.)

Ice Volcanoes on Ceres May Provide Replicators Means of Spreading

Extraterrestrial replicators (be they naturally-evolved, or von Neumann probes or the mutant descendants thereof) are at least as likely to be based on organic chemistry as on clanking iron-age technology, as is often imagined. Material returned from comet Wild-2 showed that it was actually an extraterrestrial comet, and had amino acids on it. Other investigations have shown the presence of nucleobases (the components of DNA and RNA.)

Even Arrhenius-style "panspermia" spread by passive diffusion on astronomical timescales is not implausible, as our Oort Cloud has mixed with close-passing stars' clouds on the order of once every 0.1 MA (and we should assume this happens to other stars as well.) However, for passively spreading replicators, higher-gravity bodies like planets or large moons are dead ends because they have no means of escaping the gravity well.



Water geysers on Enceladus, from space.com
This is why comets and wet carbonaceous asteroids are the best places to look, and why the Hayabusa-2 probe on Ryugu is so important. Same for the Dawn probe. Europa and even Enceladus may be a tough sell as passively escapable gravity wells, but now we see evidence of active water volcanoes on Ceres through its life span.

Implications for Panspermia: Metazoans Can Survive Freezing Under Natural Conditions

Nematodes were frozen in Siberian permafrost 42,000 years ago, and were thawed in a lab, showing behaviors like feeding. This has implications for panspermia. In another unintentional experiments, other roundworms on the space shuttle survived uncontrolled re-entry and were found on the ground weeks after the accident. Stars regularly make close passes on time scales on the order of 100,000 years. 70,000 years ago, there was a star less than a light year away (Scholz's Star.) Large meteor strikes regularly (on geological timescales) send material into space. Are there thaw-able Earth nematodes (and many other things) now in order around Scholz's Star? There are definitely extraterrestrial objects in this solar system, but only in one case have we checked for biochemistry - and we at least found amino acids.