ESA · Space

A Hitchhiker's Guide to Hera's Target Asteroids

ESA's Hera spacecraft is approaching the Didymos-Dimorphos asteroid system. This article imagines what it would be like for a human to visit these asteroids upon Hera's arrival.

Hera is heading towards two asteroids: Dimorphos, about the size of the Great Pyramid of Giza, orbits the larger, mountain-sized Didymos. Both are made of dark, silicon-rich rock with surfaces as bright as the lunar highlands. Sunlight intensity will be similar to Mars orbit.

Didymos, shaped like a spinning top, has smooth plains and rotates rapidly, suggesting Dimorphos may have broken off from it. Loose dust might be observed rising from Didymos due to its fast spin.

Dimorphos, likely reshaped by the DART impact, resembles a rubble pile asteroid with large boulders. Its gravity is about 200,000 times weaker than Earth's, while Didymos's is 40,000 times weaker.

Falling from 2 km away to Dimorphos would take two days, with a surface impact speed of only 10 cm/s. Bouncing is likely, potentially lasting hours, similar to the Philae lander's experience.

On Dimorphos, 'walking' would be difficult; gliding just above the surface might be more practical. Boulders could be unstable, and dust clouds might persist.

Visiting Didymos would require a carefully aimed jump. Its rotation counteracts its stronger gravity, creating a downward tug except at the poles. Debris from Dimorphos's impact plumes might be visible on its surface.

Human visits to these asteroids are not expected soon. These imaginative scenarios help Hera mission planners optimize instruments and spacecraft operations.

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