Nasa called on backyard astronomers and other citizen-scientists to help track asteroids that could create havoc on Earth.

The initiative aims to detect all NEOs – near Earth objects – of 30 metres or larger

The US space agency has already identified 95 per cent of the potentially planet-killing NEOs – near Earth objects – with a diameter of one kilometre or more, a size comparable to the space rock many scientists believe wiped out the dinosaurs some 65 million years ago.

Now Nasa wants to work with individuals, government agencies, international partners and academia to “find all asteroid threats to human populations and know what to do about them”. More information is available online at www.nasa.gov/mission_pages/asteroids/initiative/grand_challenge.html.

Between 50 and 100 amateur astronomers are doing what is called light-curve analysis on space rocks, making repeated images of the astronomical bodies to help determine their characteristics, said Jason Kessler, program executive for what Nasa calls Astroid Grand Challenge.

“We’re certainly going to need more help with that as our detection rate goes up,” Kessler said by telephone. He acknowledged that what Nasa aims to do, at least in part, is to crowd-source asteroid detection.

Even smaller space rocks can be dangerous, whether or not they hit the Earth. In February, a meteorite about 17 metres in diameter exploded over central Russia, shattering windows, damaging buildings and injuring 1,200 people.

Earlier this month, an asteroid the size of a small truck zoomed past the Earth four times closer than the Moon, crossing within about 105,000 kilometres over the Southern Ocean south of Tasmania, Australia.

Estimates suggest less than 10 per cent of NEOs smaller than 300 metres across have been detected, and less than one per cent of objects smaller than 100 metres in diameter have been detected, Nasa said in a statement.

The initiative aims to detect all NEOs of 30 metres or larger, Kessler said.

The space agency has also announced plans for a mission to capture a small asteroid, redirect it into a stable orbit and send humans to study it as early as 2021.

US lawmakers have also become interested in NEO. In March, the House of Representatives’ science committee held a hearing on Threats from Space that reviewed efforts to track and mitigate asteroids and meteors.