Image copyright NASA/JPL-CALTECH/MSSS Image caption Curiosity landed in Gale Crater four months ago

The US space agency (Nasa) says it will launch a new rover to Mars in 2020.

The vehicle will be based on its Curiosity robot, which landed on the Red Planet in August.

Nasa expects to re-use many of the technologies that worked so successfully in getting the one-tonne spacecraft down into the huge equatorial bowl known as Gale Crater.

This included a rocket-powered crane that lowered Curiosity to the surface on nylon cords.

The announcement of a follow-up robot was made here at the American Geophysical Union (AGU) Fall Meeting, the world's largest annual gathering for Earth and planetary scientists, and a major showcase for Nasa-led research.

It was communicated by the agency's associate administrator for science, John Grunsfeld.

"The new rover's going to be based on the [Curiosity] chassis, and it's really building on the tremendous success of the engineering of Curiosity," he said.

"It will have new instruments. We're going to put out a letter to colleagues to ask for folks who want to be in the science definition team. And the idea is to work through the winter and spring, and have an announcement of opportunity [in] mid-summer for actual instruments, because while 2020 might seem a long way off, it's really not. Curiosity was about a decade in the works."

Nasa's budget for planetary science, and Mars research in particular, has been squeezed of late, forcing the Americans to pull back on their commitments to two European Red Planet ventures in 2016 and 2018. But Mr Grunsfeld said there was scope in the financial outlook for a major mission at the end of the decade.

Media playback is unsupported on your device Media caption Nasa's John Grunsfeld speaks to Jonathan Amos about future missions to Mars

Critical to its affordability will be the intention to re-use the Curiosity template.

The 2020 rover will share many aspects of its design with the current robot, most notably its novel entry, descent and landing (EDL) system.

This included a hovering "skycrane" that was able to put Curiosity down with pin-point accuracy in Gale Crater.

The agency also has a collection of spare parts left over from the build of Curiosity. Among these is a spare nuclear battery.

"That will become the prime for the 2020 mission, and there was an engineering test unit that we will now try to upgrade to a back-up," Mr Grunsfeld said.

The budget for the 2020 vehicle will be about $1.5bn (at 2015 prices) compared with the $2.5bn quoted for the cost of Curiosity at launch last year.

John Grunsfeld has already discussed the mission with his opposite number at the European Space Agency - Alvaro Gimenez Canete - who he said was excited about the possibility of participating in the project.

"It will be an international mission as all our missions are," the former astronaut added.

Curiosity landed on Mars on 6 August. It is investigating Gale for signs that past environments could have supported microbial life.

Its major discovery so far is the realisation that it touched down in an ancient river-bed system where water once flowed, perhaps waist deep.

Given the longevity of Curiosity's nuclear battery, there is every expectation that it will still be operating when its near-copy arrives in 2021.

Image copyright NASA

(A) Curiosity will trundle around its landing site looking for interesting rock features to study. Its top speed is about 4cm/s

(B) This mission has 17 cameras. They will identify particular targets, and a laser will zap those rocks to probe their chemistry

(C) If the signal is significant, Curiosity will swing over instruments on its arm for close-up investigation. These include a microscope

(D) Samples drilled from rock, or scooped from the soil, can be delivered to two hi-tech analysis labs inside the rover body

(E) The results are sent to Earth through antennas on the rover deck. Return commands tell the rover where it should drive next

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos