IN DEEP: Researchers at the Monterey Bay Aquarium Research Institute (MBARI) deployed their benthic rover off the coast of central California this summer to test its ability to record oxygen levels in the underwater sediment and document the effects of climate change on marine life as the oceans warm.
© MBARI

While the Spirit and Opportunity rovers this summer soldiered on after more than five years on Mars (despite a number of glitches), an intrepid bot called the benthic rover created by scientists at the Monterey Bay Aquarium Research Institute (MBARI) showed its chops as a remote research vehicle by spending most of July traveling over the Pacific Ocean floor about 40 kilometers off the California coast, some 900 meters below sea level.

Robotic voyagers today give scientists the ability to continuously study remote places and phenomena previously available only in snapshots. MBARI's rover afforded researchers a close-up view of life on the deep seafloor, collecting information they're hoping will help document the effects of climate change on marine life as the oceans warm. The aquatic roamer took 18 different measurements (each one taking about a day to complete) of how much oxygen is being consumed by the community of organisms living in the ocean floor's sediment. From there, scientists hope to calculate how much food the creatures are consuming.

Although researchers are still analyzing the oxygen figures, MBARI marine biologist Ken Smith says the fact that the scientists now have so much data to work with proves the rover performed well.

Smith has been developing the benthic rover with MBARI project engineer Alana Sherman over the past four years. They designed it to creep slowly across the seabed at a rate of one meter per minute, stopping every three to five meters to examine the sediment and organisms in its path. One of the researchers' goals is to determine how deep-sea animals find enough particles of organic detritus, known as "marine snow," for sustenance in the absence of plant life.

The rover uses probes to record oxygen levels in the underwater sediment as well as acoustic scanners to sense the presence of worms and other animals as deep as 10 centimeters into the mud.

The researchers shielded the rover's electronics and batteries inside titanium pressure spheres so the vehicle could withstand 420 kilograms per square meter of water pressure. Another important feature are the large yellow blocks of buoyant foam attached to the vehicle that help support much of its 1,400-kilogram weight (making it weigh only 45 kilograms underwater) so that its tractorlike treads do not get bogged down on the seafloor.

To avoid the problem of loose sediment affecting the rover's measuring equipment, the researchers programmed the device to sense the direction of the prevailing current, and move only in an up-current direction, so that any stirred-up mud and particles would be carried away from the front of the vehicle.

During its July mission, the rover was tethered via a long cable to the Monterey Accelerated Research System (MARS) Ocean Observatory Test Bed. This provided the vehicle with power and a communications link, although the goal is to make the rover battery-operated and autonomous by year-end. "We used a cable this time so we could troubleshoot any problems," Smith says.

Once the rover is autonomous, it will store data for six months on its own. "You'll throw it off the ship, and then you send an acoustic signal demanding it to drop its weights when you want to retrieve it," Smith says. The researchers are planning at some point to outfit the rover with an acoustic modem so it can communicate information in real-time with buoys, which can then relay messages to researchers on board ships or onshore.

The rover's next mission will be to continue measuring sediment samples at its underwater stomping ground in Monterey Bay for two and a half months this fall. In 2010 the researchers plan to increase the stakes, sending their creation on a six-month crawl of the ocean floor 220 kilometers off the central California coast at a depth of about 4,000 meters (its depth limit is 6,000 meters). Success in these endeavors could see the rover sent to study the seabed near Antarctica or hooked up to a deep-water observatory several hundred kilometers off the coast of Washington State.