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.

NASA leaders, retired launch directors, families of fallen astronauts and space fans marked the 35th anniversary of the Challenger disaster on Thursday, vowing never to forget the seven who died during liftoff.

Early planetary migration in the solar system has been long established, and there are myriad theories that have been put forward to explain where the planets were coming from. Theories such as the Grand Tack Hypothesis an the Nice Model show how important that migration is to the current state of our solar system. Now, a team from Lawrence Livermore National Laboratory (LLNL) has come up with a novel way of trying to understand planetary migration patterns: by looking at meteorite compositions.

The researchers, led by postdoc Jan Render, had three key realizations. First, that almost all the meteorites that have fallen to Earth originated from the asteroid belt. Second, that the asteroid belt is known to have formed by sweeping material up from all over the solar system. And third, and perhaps most importantly, that they could analyze the isotopic signatures in meteorites to help determine where a given asteroid had formed in the solar system.

With that knowledge, they could then extrapolate out to other asteroids of the same type. There are approximately 100 different types of asteroids, with different isotopic signatures, in the asteroid belt.

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.