A spiral galaxy imaged by the Hubble Space Telescope. Image credit: NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team (STScI/AURA)

Mars is covered in craters, but most of them are very old. But new ones do appear from time-to-time, created when objects hit the surface of the red planet. That’s just what happened at some point a couple of years ago, producing one of Mars’ youngest craters. Higher up in Mars’ atmosphere, scientists are also learning about the role the micrometeorites play in forming clouds. And how can the Moon reveal secrets about history of the Sun?

Closer to home, there has been controversy about once of the latest SpaceX launches, which released 60 satellites into orbit as part of the Starlink “constellation”. While impressive, and part of plans for over 10,000 such satellites in orbit, there has been some opposition from astronomers, for whom satellites are a constant irritation. But to the ends (worldwide satellite internet) justify the means? Chris North and Edward Gomez discuss.

Meanwhile, over a million volunteers have been clicking away on the Galaxy Zoo website, part of the Zooniverse. Chief zookeeper Prof Chris Lintott explains what astronomers have discovered as a result of all this effort. It’s overturned commonly held views about the shapes of spiral galaxies, both in their beautiful spiral arms and their central bulges. The result is that we might be able to get a better understanding of the how spiral arms behave when two galaxies get close together.

An extended edition of an original broadcast on 4th July 2019 as part of Pythagoras’ Trousers on Radio Cardiff.