A 1970s Soviet rover
did indeed travel about 3 miles farther on the surface of the moon than
originally thought, meaning that any robot hoping to break its off-world
distance record will have to run a full marathon, researchers say.
The remote-controlled
Lunokhod 2 moon rover was long thought to have traveled 23 miles (37
kilometers) on the lunar surface back in 1973. But a Russian team recently
upped the estimate to 26 miles (42 kilometers), using images snapped by NASA's
sharp-eyed Lunar Reconnaissance Orbiter.
The Russian
researchers, led by Irina Karachevtseva of the Moscow State University of
Geodesy and Cartography, have been presenting the new number at conferences for
the past year or so. But the revision began attracting widespread attention
only in the last month, as NASA's Opportunity Mars rover crept closer and
closer to the old 23-mile mark. [Distances Driven on Other Worlds
(Infographic)]
Now a second group of
scientists — who are affiliated with the Lunar Reconnaissance Orbiter Camera
(LROC) instrument suite — has backed the Russian team's finding, also using
LROC images of Lunokhod 2's tracks to come up with an independent estimate
around 26 miles.
"I think it's 41.5
[kilometers] or something like that, but we're not done yet," LROC
principal investigator Mark Robinson, of Arizona State University, told
SPACE.com on Monday (July 8). "We'll actually have a featured image fairly
soon on the LROC web page that gives that number."
The LROC team is
conducting its analysis as a simple double-check, not because it doubts the
number derived by Karachevtseva and her colleagues, Robinson said.
"There isn't
really a controversy here," he said. "We can measure the exact
distance traveled by the rover now that we've got these pictures."
The LROC images, which
boast a resolution of 1.6 feet (0.5 meters) per pixel, were unavailable back in
Lunokhod 2's day, of course. The Lunar Reconnaissance Orbiter launched in 2009,
36 years after the old Soviet rover rolled to its final stop on the moon.
The original estimate
of 23 miles appears to be based on the distance between Lunokhod 2's start and
end points, Robinson said. But LROC photos show that the robot backtracked
several times and also occasionally traveled in circles in order to take
panoramic photos, adding several miles to its total odometry.
So Opportunity has a
ways to go before it can be crowned the off-world driving champ. As of
Wednesday (July 10), the rover had traveled 23.35 miles (37.58 km) since
touching down on Mars in January 2004 along with its twin, Spirit, to hunt for
evidence of past water activity.
And Opportunity will
soon be hunkering down in a location called Solander Point to wait out the
harsh Red Planet winter, so Lunokhod 2's record is likely safe for a while yet.
But pitting the
Opportunity rover against Lunokhod 2 doesn't make much sense to Robinson. After
all, the two robots are very different beasts that explored different world’s
decades apart. And Lunokhod 2 covered all that ground in less than five months,
he noted, while Opportunity has been chugging along for more than nine years.
Robinson wishes people
would stop fixating on the distance record and take a little time to appreciate
what both rovers managed to achieve on their separate missions.
"They've both
accomplished amazing things, so focusing on who drove the farthest is really
not useful," Robinson said.
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