Nasa announcement: Mission to send spacecraft to Saturn's moon Titan revealed - as it happened

Hello and welcome to our live coverage of today's "major" Nasa announcement.

Proceedings will commence at 4pm EDT (9PM BST) and will air on NASA Television, the agency's website, Facebook Live, YouTube, Periscope and USTREAM.

NASA also will host a media teleconference at 5pm local time the same day with:

Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate

Lori Glaze, director of NASA’s Planetary Science Division

Curt Niebur, Lead Program Scientist for New Frontiers

Principal investigator of the selected mission

Here is the full story previewing the announcement:

Nasa has been sparing with the details of the announcement, which has led some to speculate based on the members of the invited panel.

This is still very much unconfirmed, but rumours suggest it could be one of two missions: either to extract samples of a comet nucleus and return them to Earth, or a journey to Saturn’s largest moon, Titan.

That stems from the fact that Curt Niebur, lead scientist for the New Frontiers programme, is one of those taking part.

In 2017 Nasa announced it had selected two concepts for a robotic mission planned to launch in the mid-2020s under the New Frontiers banner.

The first was a Comet Astrobiology Exploration Sample Return (Caesar) mission that seeks to return a sample from 67P/Churyumov-Gerasimenko, a comet that was explored by the European Space Agency’s Rosetta spacecraft, to determine its origin and history.

The second was Dragonfly, a drone-like aircraft that would explore the habitability of dozens of sites on Saturn’s moon Titan, described by Nasa as an "ocean world in our solar system".

Nasa made another important announcement yesterday, revealing moon rock samples collected by Apollo astronauts and subsequently locked away by for decades are to be examined by researchers. Here is the full story:

On Tuesday, a series of Nasa experiments were launched into space on board the SpaceX Falcon Heavy rocket, which blasted off from the Kennedy Space Center in Florida.

Among them was Nasa's Deep Space Atomic Clock, a toaster oven-sized instrument that will test a new way for spacecraft to navigate in deep space.

Also part of the launch was the Green Propellant Infusion Mission, which will test a new propulsion system that runs on a high-performance and non-toxic spacecraft fuel.

Nasa's Curiosity rover has discovered high amounts of methane gas on the surface of Mars that suggests the possibility of alien life on the planet.

The discovery of the gas is significant because on Earth methane is usually produced by living things.

Here is the full report from earlier this week.

Just in case you want to see what you can read into it, here's what Nasa said in its announcement of the announcement:

"NASA will announce a major new science mission to explore our solar system during a broadcast of NASA Science Live at 4 p.m. EDT Thursday, June 27."

And here's who will be going to the press conference at 5pm:

• Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate
• Lori Glaze, director of NASA’s Planetary Science Division
• Curt Niebur, Lead Program Scientist for New Frontiers
• Principal investigator of the selected mission

30 minutes until everything kicks off. It'll probably be very shortly after that when we'll find out which of the proposals has won – Nasa isn't usually the kind to keep people waiting.

While we're waiting for everything to kick off, have a look at this huge mobile launcher driving along on its way to a launch pad.