At some point between 300 million and 1 billion years ago, a large cosmic object smashed into the planet Venus, leaving a crater more than 170 miles in diameter. A team of Brown University researchers has used that ancient impact scar to explore the possibility that Venus once had Earth-like plate tectonics.

For a study published in Nature Astronomy, the researchers used computer models to recreate the impact that carved out Mead crater, Venus's largest impact basin. Mead is surrounded by two clifflike faults—rocky ripples frozen in time after the basin-forming impact. The models showed that for those rings to be where they are in relation to the central crater, Venus's lithosphere—its rocky outer shell—must have been quite thick, far thicker than that of Earth.

In recent years, satellites have become smaller, cheaper, and easier to make with commercial off the shelf parts. Some even weigh as little as one gram. This means more people can afford to send them into orbit. Now, satellite operators have started launching mega-constellations—groups of hundreds or even thousands of small satellites working together—into orbit around Earth.

Instead of one large satellite, groups of small satellites can provide coverage of the entire planet at once. Civil, military and private operators are increasingly using constellations to create global and continuous coverage of the Earth. Constellations can provide a variety of functions, including climate monitoring, disaster management or digital connectivity, like satellite broadband.

But to provide coverage of the entire planet with small satellites requires a lot of them. On top of this, they have to orbit close to Earth's surface to reduce interruption of coverage and communication delays. This means they take up an already busy area of space called low Earth orbit, the space 100 to 2,000km above the Earth's surface.