But the delayed arrival was not all bad: NEAR Shoemaker successfully flew within 2,375 miles (3,830 km) of the asteroid and snapped over 200 photographs. That flyby helped reveal that Eros is smaller than was predicted, has at least two medium-sized craters, has a 12-mile (20 km) ridge, has a surface density roughly comparable to Earth’s own crust, and rotates once every 5.3 hours. Yet, despite obtaining that valuable information, failing to achieve orbit proved a bitter pill to swallow.
Fortunately, the delay did not mean that an orbital mission was out of the question, and efforts were already underway for another attempt the following year.
Finally, despite suffering a computer reset, weathering the hyped Y2K software bug, and enduring another far-from-perfect engine firing, on the first Valentine’s Day morning of the new millennium, NEAR Shoemaker slipped into orbit around a celestial object named after the god of love.
Shoemaker sets up shop on Eros
Over the next few months, NEAR Shoemaker circularized its orbit and approached Eros, coming within about 22 miles (35 km) of the asteroid’s surface. During this time, it globally mapped the ground and examined peculiar ridges, square-shaped craters, boulders, surface grooves, and trough-like depressions. Then, by January 2001, as it nearly brushed the edge of Eros at an altitude of just 1.7 miles (2.7 km), hopes of a soft landing on the asteroid’s surface entered the realm of possibility.
“This is a bonus,” mission director Robert Farquhar of Johns Hopkins University Applied Physics Laboratory cautioned at the time. “The descent maneuvers are the most complicated we’ve ever tried, and because the spacecraft is an orbiter that wasn’t designed to land, there is only the smallest chance it will survive on the surface of Eros.”
Over the course of 4.5 hours on February 12, 2001, NEAR Shoemaker executed its nail-biting descent with its camera pointed down to reveal the steady, inexorable approach of the surface. Landing, when it came, was surprisingly gentle, touching down at about 4 mph (6.4 km/h). NEAR Shoemaker also came to rest remarkably close to an interesting saddle-like depression called Himeros.
As the probe floated silently towards Himeros, it scrutinized this Key West-sized surface feature, which looked like part of a large impact crater. The last photograph of the site was taken less than 400 feet (120 m) above the surface, revealing a patchwork of pebble-strewn terrain, fragmented boulders, and a dust-filled crater the size of a football field. But Farquhar’s caution was well founded, for the landing was indeed the spacecraft’s curtain call.
NEAR Shoemaker finally went radio quiet on February 28, 2001.
Since then, several other missions — NASA’s Stardust, New Horizons, and Dawn; Europe’s Rosetta; and China’s Chang’e-2 — have gone on to examine near-Earth objects, main-belt asteroids, and trans-Neptunian bodies. And just last December, Japan’s Hayabusa-2 even returned samples from asteroid Ryugu to Earth, which scientists are now eagerly inspecting. Also chomping at the bit is NASA’s OSIRIS-Rex mission, which last October sampled asteroid Bennu. The mission aims to return those specimens to Earth in September 2023.
And there’s plenty more to come, too. In October of this year,
NASA’s Lucy mission will set off on a decade-long trek to visit a half-dozen Jupiter-trailing Trojan asteroids. Next year, China’s ZhengHe spacecraft will fly a sample-return mission to the rapidly rotating near-Earth asteroid Kamo’oalewa. And also in 2022, NASA’s Psyche will head for a metallic asteroid of the same name.
It has been 20 years since NEAR Shoemaker made history by cuddling up with asteroid Eros just two days before Valentine’s Day. And that unexpectedly successful date kicked off a continuing quest to unlock the secrets of these tiny worlds, as well as the clues they might hold about how we came to be.