News

It's 2026 and a space capsule gently nudges toward its destination. Through a side window, Earth and its moon look like tiny, gleaming crescents, distant dancers in a sea of night. But all eyes are glued on the mesmerizing sight that looms ahead.

For weeks, it has been too tiny to spot; now, the little rock has grown to fill the capsule's view. It's a 30-storey behemoth, bulging and bending at weird angles, with sharp boulders projecting like shark fins from pools of fine-ground rubble. Recalling past moon landings, the rock's alien terrain looks stark and grey. But this place feels nothing like the moon.

Welcome to asteroid country.

If you've been looking forward to seeing a human on the moon again, then this has been a bad month.

Faced with mounting deficits and war abroad, President Barack Obama has frozen discretionary spending across the U.S. government. Last week, the spotlight was on the National Aeronautics and Space Administration, as Mr. Obama proposed not merely trimming budgets at the space agency but cancelling a high-profile project to return astronauts to the moon announced by George W. Bush in 2004.

Its cancellation means there are no immediate plans to travel beyond low Earth orbit. Critics say the move guts the human space program and will cost thousands of jobs.

Yet, for some, there could be a potential silver lining: With the moon off the table, NASA is free to move in other directions. “If you have the capability of going to the moon, you have the capability of going to other places,” says Paul Abell, a Canadian research scientist at NASA's Johnson Space Center in Houston – other places such as near-Earth asteroids.

Largely ignored in the early days of the space program, these flying relics from the formation of the solar system are commanding heightened attention these days, both as objects of scientific interest and as potentially lethal hazards.

The moon may have reams of unfinished business for explorers, but for the general public it sits firmly in the “been there, done that” category. But a manned asteroid mission represents something truly novel.

“You are actually getting beyond the Earth-moon system and exploring places that are entirely new worlds,” says Dr. Abell, who works in the building that houses NASA's moon rocks, but for years has set his sights on the “target-rich environment” of bigger rocks that whiz by our planet.

He and engineer Rob Landis have identified more than 40 small asteroids that pass near enough to Earth at the right speed to allow for a short visit by a three-person crew some time between 2020 and 2035. “It would be anywhere from a three-to-five-month mission,” Mr. Landis says, “with a week to two weeks spent at the asteroid.”

Martin Ratcliffe, director of development with the planetarium maker Sky-Skan, has acquired a keen sense of what inspires public enthusiasm about space. When NASA invited him to work on a visualization of an asteroid mission, he immediately grasped the appeal of such "stepping stones on the way to Mars and beyond.”

Americans, he adds, have lost their sense of urgency about the moon. But asteroids pack plenty of urgency, because of their dangers. Although they are mostly confined to the asteroid belt between the orbits of Mars and Jupiter, they can be scattered by collisions and by gravitational tugs from the various planets. This creates a steady supply of asteroids that periodically cross Earth's orbit.

“ It will happen. It's just a matter of time.”

— Dr. Paul Abell, Canadian research scientist with NASA

Most will eventually fall into the sun, but some will collide – with devastating consequences for life. It is now widely accepted that the impact of a 10-kilometre-wide asteroid 65 million years ago coincides with the disappearance of the dinosaurs along with most of the animal species on Earth at the time.

Extinction-causing impacts would be extremely rare, because most Earth-crossing asteroids are not that large. However, even an asteroid as small as 140 metres across could trigger a major catastrophe, and cost millions of lives depending on where it strikes.

Recent estimates suggest at least 50,000 asteroids orbiting near Earth are above that size threshold, and as many as 20 per cent have potentially hazardous trajectories. (The head of the Russian space agency has already called for action on asteroid Apophis, at risk of hitting Earth after 2030.)

“As a civilization,” Mr. Ratcliffe says, “we really need to tackle the question of how we divert an asteroid.”

Asteroid missions have been touted as a way of getting to know the enemy – a detailed look at how asteroids are put together, and a chance to test strategies for deflecting them when necessary.

“You can imagine placing a detonation device on the asteroid as an experiment and then triggering it once the astronauts have left,” Mr. Landis says.

Instruments deployed on the asteroid would provide a precise measure of how the energy of the explosion affected the motion of the asteroid, all of which could prove invaluable if another asteroid were bearing down on Earth.

Since 2005, Congress has charged NASA with finding 90 per cent of the asteroids that could pose a threat in the foreseeable future, but a study issued last month found the space agency lacked the resources. Mr. Obama's NASA budget includes significant increases for that search, and money for the development of heavy-lift rockets that could make missions to asteroids a reality.

“If there's money for a heavy-lift vehicle, that indicates human space flight,” Dr. Abell says.

Although an asteroid mission might take humans 20 times farther from Earth than the moon, it would cost less than a lunar mission, which requires a separate, fuelled-up lander that can escape the moon's gravity when it's time to depart. Small asteroids have almost no gravity to speak of so a close encounter would be not so much a landing as a docking.

Astronauts would be tethered to their mother ship and might travel hand over hand across the asteroid's surface like nimble rock climbers scaling a cliff. There would be no blast-off at the end of the visit – just a cast-off and an about-face home.

However, Mr. Landis is quick to point out that an asteroid mission would not be easy. It would require far longer travel times than a moon mission, exposing astronauts to much higher doses of solar and cosmic radiation. It would also be far enough away to prohibit easy communication with Earth. The two-way signal delay between spacecraft and mission control could stretch to nearly a minute, leaving astronauts effectively on their own when it comes to manoeuvring their craft and responding to emergencies.

Some of the risks would be mitigated by robotic missions that would scout out candidate asteroids, assessing the feasibility and value of a human mission. But while robots can do many things, including bringing samples of an asteroid back to Earth, a human astronaut could do more.

“The obvious advantage to having people there is the ability to adjust in the face of new discoveries,” says Alan Hildebrand of the University of Calgary, who is heading up a project to detect more near-Earth asteroids with Neossat, a Canadian satellite.

Although the Canadian Space Agency is not officially considering human missions to asteroids, there is little doubt that Canadian space technology and expertise could contribute to such a venture. In a climate of austerity, NASA would welcome international partners.

All of this gives a human asteroid mission more sustainable momentum than a return to the moon could ever hope to achieve. “It will happen. It's just a matter of time,” Dr. Abell says. “Within my lifetime, it's almost a certainty." If he is right, the next humans to set feet – or hands – on another world may already be in high school. Meanwhile, the strange place they will some day encounter waits patiently in the shadows.