Astronomers have now spotted a second mysterious, likely interstellar object on a path through our solar system.

These interlopers — the first of which came through the inner solar system in 2017 — represent the best chance astronomers have so far of learning more about far off star systems from close range.

• "This is the only thing in astrophysics where you a have a piece of the galaxy come to you," planetary astronomer Michele Bannister told Axios.

What's happening: Last week, scientists announced the discovery of a likely interstellar comet.

• NASA right now predicts the comet will fly about 190 million miles from the Sun during close approach in December before heading out of the solar system again.
• Unlike 'Oumuamua, the first interstellar object, this comet — C/2019 Q4 (Borisov) — will be visible for about a year, giving astronomers time to study its structure, composition and path through the galaxy.

Details: Some scientists will be focused on the comet's atmosphere, known as a coma, that is created when the object heats up as it nears the Sun. The heat causes ice on the comet to turn immediately from a solid to gas.

• Scientists hope to piece together what kinds of ice exist on the comet — and the amount — by watching how sunlight hits the coma.
• Early results from observations taken by the Gran Telescopio Canarias show that C/2019 Q4's composition may be similar to the comets seen in our solar system.
• If the comet's chemistry matches what astronomers have found in comets elsewhere in our solar system, it could indicate that the part of space where the comet formed might be similar to our solar system's chemistry.

"This, to me, has bearing on, 'Are all solar systems suitable to life?'" Karen Meech, an astronomer at the University of Hawaii, told Axios.

Background: Scientists are hoping to compare 'Oumuamua and C/2019 Q4 to figure out just how different or similar the 2 objects coming from 2 parts of the galaxy are.

• In particular, they'll attempt to compare C/2019 Q4's shape to the odd cigar-like structure of 'Oumuamua, which looked different from anything we've yet seen in our solar system.

Some scientists hope to create a protocol for whenever the next interstellar comet is found in order to maximize their chances to observe it as soon as it's seen.

• The Large Synoptic Survey Telescope, expected to come online next year, should be able to spot interstellar objects as they fly through our solar system.
• The European Space Agency's Comet Interceptor mission — expected to launch in 2028 — could intercept an interstellar comet when it's in place and ready after its expected launch in 2028.

The big picture: Even without those new tools online, catching sight of C/2019 Q4 just 2 years after seeing 'Oumuamua already deepens the mystery around just how many of these interstellar objects might be visiting our solar system.

• It's possible these objects pass through our solar system more often than scientists originally thought, but with just 2 seen so far scientists can't say whether that's definitively the case or not.
• "Maybe our understanding is different. Maybe we're just super lucky. Maybe there's a new mystery here. We don't know," space scientist Carrie Nugent told Axios.

Relativity Space and Momentus — 2 companies looking to capitalize on the growing small satellite industry — are teaming up.

Driving the news: Relativity — which is trying to create the world's first fully 3D printed rocket — plans to launch satellites using Momentus' space tug system to orbit for the first time in 2021.

• From its initial orbit, Momentus' shuttle system will further propel these small and medium-sized satellites to their final destinations in geosynchronous orbit.
• The companies said there is an option for 5 more possible launches.

The big picture: Euroconsult predicts the small satellite manufacturing and launch industry will grow to $42.8 billion from 2019 to 2028, nearly quadrupling in size.

Where it stands: By signing this agreement, Momentus and Relativity hope to provide access to more orbits for their customers, once they begin flying.

• Typically, small satellites get to space by hitching a ride on large rockets with big payloads. Those small spacecraft are usually delivered to orbits that many satellites can use.
• Momentus' system is designed to bring satellites out to other, more specialized orbits after launch, saving their customers money that would have been spent on a dedicated launcher.
• Relativity is attempting to break into the increasingly crowded small launcher industry by differentiating itself as a new kind of flexible, responsive rocket company.

Yes, but: Some experts are concerned a bubble is forming in the small rocket industry, with dozens of companies hoping to come online in the coming years.

• Relativity Space — which expects to launch its first rocket next year or early 2021 — sees the flexibility its 3D printing affords as a huge advantage in the market.
• "The printing tech can be extended," Jordan Noone, CTO of Relativity Space, told Axios. "A factory we have today could be making a fleet of rockets this week and then a fleet of airliners or drones next week."

Saturn's rings may be more ancient than previously thought, according to a new analysis published in the journal Nature Astronomy this week.

Why it matters: The true age of the rings has major implications for the age of Saturn's moons.

• Many scientists think that Saturn's moon Enceladus is one of the places in our solar system most likely to host life, but if the moon is young, life may not have had enough time to develop.

What they found: Earlier studies have suggested that the rings are young, at about 10 million–100 million years old, based on estimates of their mass and appearance.

• The rings themselves — which are thought to have been formed from water-ice — don't show evidence of a ton of pollution from meteoroids and dust falling onto the rings, suggesting a young age based on the rate of pollution expected from Cassini data.
• However, the new study shows that it's possible that the rings just appear to be young: The bombardment rate of the rings by pollution may just be higher today than it was in the past, or the rings are able to somehow clean themselves over time, making them look younger than they are.
• The analysis also suggests that the total mass of the rings today is more in line with models that produce an ancient system of rings around Saturn.

What's next: The mystery surrounding the age of Saturn's rings may never be solved definitively, but learning more about their eventual fate may be easier than piecing together its past, astronomer James O'Donoghue, who is unaffiliated with the new study, told Axios via email.

• O'Donoghue and his team have calculated that, based on the rate that the ring particles are "raining" into Saturn's atmosphere, the planet's most distinctive feature only has about 300 million years left before they fade away.

Bigelow's next-generation inflatable space habitat is shooting for the Moon (Loren Grush, The Verge)

NASA cubesat to test lunar Gateway orbit (Jeff Foust, SpaceNews)

Most massive neutron star ever detected strains the limits of physics (Ashley Strickland, CNN)

For NASA contractors, lunar landing failures by Israel and India hit close to home (Christian Davenport, Washington Post)

Water vapor detected in the atmosphere of a super-Earth (Axios)

A fleet of satellites orbiting Mars allows us to see the changing face of the Red Planet throughout the year, and sometimes its surface looks remarkably similar to Earth.

• A photo taken in May by NASA's Mars Reconnaissance Orbiter shows an avalanche of ice falling on the planet.
• "Every spring the sun shines on the side of the stack of layers at the North Pole of Mars known as the north polar layered deposits. The warmth destabilizes the ice and blocks break loose," NASA said in an image description.
• "When they reach the bottom of the more than 500 meter tall cliff face, the blocks kick up a cloud of dust."

The MRO has been beaming back photos of Martian geology since its arrival in orbit around the planet in 2006.