Image copyright NASA Image caption The Nasa spacecraft hurtles towards its target, nicknamed 1999 JU3
NASA has launched a spacecraft to crash into an asteroid in the hopes of learning more about its size and composition.
The Europa spacecraft is aimed at studying the Jupiter-size moon Europa, believed to be made of potentially rich ice and rock deposits.
At the same time, it will crash into a roughly 12m-wide (39ft) piece of an asteroid to study its small size and rotation.
Scientists think the asteroid will burn up in the atmosphere and evaporate into space.
The $1.1bn (£842m) spacecraft, named OSIRIS-REx, will blast off from Cape Canaveral, Florida, on Monday evening (UK time) aboard a United Launch Alliance Atlas V rocket.
The spacecraft itself will not enter a “graveyard orbit” of the planet circling far from its solar panels.
The piece of asteroid – named 1999 JU3 – will be deliberately hit by a probe directed by a spacecraft named C/2008 YU3, which is already orbiting its target.
Image copyright NASA Image caption The scientists will not be able to see the impact
Working from the ground, scientists will be able to see the long run of the spacecraft before and after it hits the asteroid. The impact will last a few seconds.
Scientists hope the mission will also enable them to learn more about the pristine Earth-like asteroids, that could reveal new information about how the planets in our solar system formed.
Professor Will Grundy, director of the Planetary Science Institute in Tucson, Arizona, who is not involved in the mission, told BBC News: “There are planetary defence in Earth’s long-term future, but also asteroids in our solar system that we need to understand better.”
“The idea is to have a more effective, continuous response to our fear of asteroid impact.
“It might be advisable in the short term to make the orbit of some asteroids more complicated to understand and reduce its opportunity to impact our planet.”
Europa orbits Jupiter about 4.5billion miles (7.2billion km) away, and scientists are hoping its ocean could hold water and organic compounds that could form life.
Scientists do not know much about the moon’s composition, except that it is thought to have an icy core.
Image copyright NASA Image caption A model of the NASA spacecraft shows how it will hit the asteroid
As a moon of Jupiter, it has all the planet’s gravity, which means it would be impossible to get any further away from Jupiter than 5m.
Its orbit is so tightly sealed that it has escaped damage from Jupiter’s massive gravitational forces and its chemicals and ice have remained largely intact for billions of years.
It has also survived bombardment by asteroids and comets.
The search for clues about its composition and structure will use a suite of instruments aboard the OSIRIS-REx spacecraft.
These include radar instruments for mapping the moon’s surface, a coronagraph to block out any light from Jupiter itself, a laser altimeter to measure gravity and magnetic fields, and a spectrometer to analyze a sample of debris recovered from the surface.
The spacecraft will pass by Jupiter on 3 August 2019, returning samples of particles and organics in a lab on the ground by 2023.
Europa – once was a full-fledged satellite of Jupiter – was battered off its icy shell by violent impacts in its youth.
This may explain why it has remained so intact and how much water is contained within its ice layer, researchers say.
Nasa plans to return a sample to Earth in 2023, transported by the mother spacecraft back up through space to near the moon’s orbit.
The OSIRIS-REx mission is one of five missions that are being funded by the agency’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) programme.
Called by the Spanish acronym, it is the largest programme between the US and Spain since the discovery of Neptune.
Material taken from the asteroids will return to Earth and the moon in 2023, but it will take much longer to sample from the plumes of water droplets believed to exist under the surface of Europa.