Nasa announcement live: Latest updates as space agency reveals solar system discovered with artificial intelligence

We know very little for sure about what Nasa is about to announce. But from those few clues we can make some guesses about what it might cover – here's my attempt at doing that.

Some other important Nasa news, ahead of the big announcement: the agency has just announced that its astronaut Randy Bresnik has returned to Earth with two of his crewmates. They'll be sending another one up, with two more crewmates, on Sunday.

Here's the AP's report on those three astronauts coming back down to Earth:Three astronauts on Thursday landed back on Earth after nearly six months aboard the International Space Station.A Russian Soyuz capsule with NASA's Randy Bresnik, Russia's Sergey Ryazanskiy and Paolo Nespoli of the European Space Agency descended under a red-and-white parachute and landed on schedule at 2:37 p.m. local time (0837 GMT; 3:37 a.m. EST) on the vast steppes outside of a remote town in Kazakhstan. The three were extracted from the capsule within 20 minutes and appeared to be in good condition. Bresnik, Ryazansky and Nespoli spent 139 days aboard the orbiting space laboratory. The trio who arrived at the station in July contributed to hundreds of scientific experiments aboard the ISS and performed several spacewalks. They left Alexander Misurkin, commander of the crew, and two Americans, Joe Acaba and Mark Vande Hei, in charge. During their stay at the station, the crew had a phone call with Pope Francis who talked with the cosmonauts about Dante's verses and St. Exupery's "The Little Prince." Bresnik, a U.S. Marine who flew combat missions during the Iraq war, told the pope what strikes him is that in space there are "no borders, there is no conflict, it's just peaceful." Kentucky-born Bresnik also celebrated Thanksgiving in space, feasting on pouches of turkey with his colleagues. The orbiting lab's crew of three will go back to a six-member team when NASA's Scott Tingle, Russia's Anton Shkaplerov and Japan's Norishige Kanai take off from Kazakhstan on Sunday.

We don't know very much about the announcement later on. But one thing we do know for sure is that it will involve the Kepler space telescope, one of the pieces of kit that Nasa is most proud of.The telescope works by surveying the whole sky and logging when any stars get brighter or darker, which happens when a planet passes in front of them. If that's happening, then the brightness can be watched over time – and by studying the dimming, they can work out a whole host of things like how big it is and how close it might be to its star.Once, finding just one planet with this method was a huge breakthrough, and before that it was something that scientist scould only dream of. But now it has become something of a commonplace – it regularly verifies hundreds of planets, though only some of them will be interesting or potential habitats.

Similar announcements in the past have yielded some of the most incredible parts of what we know about the universe. In February, for instance, scientists announced an entire solar system of exoplanets relatively near our own; in October it said it had found 20 new planets that could support life.It's found so many that the big announcements only relate to the really exciting stuff, since Kepler has now spotted thousands of exoplanets.

While we wait for Nasa's big announcement, here's some news from the Press Associaton about evidence of a meteorite that landed in the UK. (Nasa are involved, but it's not connected to today's announcement. As far as we know!)

Geologists have found evidence that a meteorite hit the Isle of Skye around 60 million years ago.

They made the discovery while exploring volcanic rocks on the island which they thought were volcanic flow deposit.

When they analysed the rock they discovered it contained rare minerals from outer space - vanadium-rich and niobium-rich osbornite, which have never been reported on earth.

The minerals have, however, been collected by Nasa's Stardust Comet Sample Return Mission as space dust in the wake of the Wild 2 comet.

A second site, seven kilometres away, proved to be a two-meter-thick layer of ejecta - material ejected from a crater - with the same strange mineralogy.

At the first site, at An Carnach on the Strathaird Peninsula, the geologists zeroed in on a meter-thick layer at the base of a 60-million-year-old lava flow which they thought was an ignimbrite (a volcanic flow deposit).

Dr Andrew Beard of the Earth and Planetary Sciences Department at Birkbeck, University of London, was one of the co lead-authors of the paper.

He said: "When we discovered what it was we were very surprised and it was a bit of a shock because we were not expecting that.

"We initially considered it to be volcanic rock so it was a bit of a shock when we realised what we had found."

Dr Beard said it was worth the arduous trek to the first site which was in a recess at An Carnach.

He said: "It took us about two hours to get to the site. we could see in the distance that there was a recess at the base of the cliff and if you get a recess it usually shows there is a different type of rock there.

"We persevered across horrendous terrain and crawled up the slope to the recess."

The researchers pin the impact to sometime between 60 million and 61.4 million years ago.

Lead co-author Dr Simon Drake, an associate lecturer in geology at Birkbeck, University of London, said it was hard work crossing the boggy terrain to reach the site.

He said: "We were sinking in up to our thighs. I distinctly recall saying to Andy Beard, 'this had better be worth it'. It was worth it."

The team published their discovery in Geology this week.

The second site was south west of Broadford.

Researchers said the discovery is the first meteorite impact described within the British Paleogene Igneous Province (BPIP) and raises questions about the impact and its possible connection to Paleogene volcanic activity across the North Atlantic.

Dr Drake has collected samples from another site on Skye that also yield strange mineralogy, including another mineral strikingly similar to one found in comet dust.

Just an hour left to go now. As a reminder, the press conference kicks off at 6, UK time – though everything else will probably go online at the same time.

Tonight isn't likely to be aliens. But that, of course, is what a lot of people hope for.So while you're waiting, why not have a read of some other recent maybe aliens news. Is there extraterrestrials living in our own solar system? What about aliens bugs being carried to Earth? Or why scientists are scanning a mysterious, unknown object that flew through our own solar system – just in case it's alien technology?

Just a reminder that you can use the #askNASA hashtag if you'd like to ask questions online. Some of them might be asked during the Q&A session on the livestream.

After the press conference is over – at 3pm eastern time or 8pm in the UK – Nasa will be hosting an AMA on Reddit. You can find that here, and get your questions in now.