One small step, Carl Zimmer

Discover, January 31, 1995

The spidery robot named Dante first tried to make history in January 1993 by descending into an Antarctic volcano, only to have its communication tether snap after 20 feet. Last August, Dante erased most of that embarrassment successfully scrambled down into the crater on Mount Spurr, a volcano 80 miles west of Anchorage, Alaska. Granted, the robot had to be rescued on the return trip, when it tipped over 350 feet short of the crater rim. But a stumble on the homestretch was distinctly better than barely getting out of the starting block–especially given the challenging terrain.

“On a difficulty scale 0 to 10, we were prepared for a 10,” said John Bares, a civil engineer who led the robot’s $1.7 million redesign at Carnegie Mellon. “But once Dante got started, was clear we were dealing with a 12.”

Steadied by a cable anchored on the crater rim, the ten-foot-long robot inched its way down the 30-degree incline, struggling to stay on top of the snow and muddy ash with the help of circular snowshoes. It also had to contend with boulders that had been shot up the crater rim during Mount Spurr’s last eruption, in 1993. Perched precariously in the muck, they often slipped and came crashing down past the robot–or onto it, in the case of one basketball-size rock.

But Dante II soldiered on, its descent monitored via satellite by Bares and his colleagues, who were sitting in Anchorage. The distance was intentional–the robot’s a rough prototype for one that might someday explore another planet. Dante II relayed video images back to Anchorage, along with a 3-D map it made by periodically scanning its surroundings with a laser. If the terrain was not too difficult, the robot would proceed autonomously in the direction it had been told to move; but when necessary the researchers could control it directly. Once on the crater floor, the robot analyzed gases escaping from the volcanic vents, mostly to show that it could.

The return trip proved more dangerous. Warm weather during Dante’s weeklong stay in the crater melted six feet of snow, exposing three previously hidden boulders in its path. Unable to scale them, the robot backed away, stepped on some particularly soft ash, lost its balance, and fell over, as helpless as a bug on its back. When a helicopter tried to lift Dante out by its cable, the cable broke, tumbling the robot another ten yards downhill. Finally, Bares and an Army soldier walked down into the crater and wrestled the robot into the helicopter’s sling. Says Bares, “Dante needs a few more versions before it’s ready to be built for space.”