[meteorite-list] Breaks Observed in Mars Curiosity Rover Wheel Treads

[Ron Baalke]

https://www.jpl.nasa.gov/news/news.php?feature=6785

Breaks Observed in Rover Wheel Treads
Jet Propulsion Laboratory
March 21, 2017

Mars Science Laboratory Mission Status Report

A routine check of the aluminum wheels on NASA's Curiosity Mars rover 
has found two small breaks on the rover's left middle wheel-the latest 
sign of wear and tear as the rover continues its journey, now approaching 
the 10-mile (16 kilometer) mark.

The mission's first and second breaks in raised treads, called grousers, 
appeared in a March 19 image check of the wheels, documenting that these 
breaks occurred after the last check, on Jan. 27.

"All six wheels have more than enough working lifespan remaining to get 
the vehicle to all destinations planned for the mission," said Curiosity 
Project Manager Jim Erickson at NASA's Jet Propulsion Laboratory, Pasadena, 
California. "While not unexpected, this damage is the first sign that 
the left middle wheel is nearing a wheel-wear milestone,"

The monitoring of wheel damage on Curiosity, plus a program of wheel-longevity 
testing on Earth, was initiated after dents and holes in the wheels were 
seen to be accumulating faster than anticipated in 2013. Testing showed 
that at the point when three grousers on a wheel have broken, that wheel 
has reached about 60 percent of its useful life. Curiosity already has 
driven well over that fraction of the total distance needed for reaching 
the key regions of scientific interest on Mars' Mount Sharp.

Curiosity Project Scientist Ashwin Vasavada, also at JPL, said, "This 
is an expected part of the life cycle of the wheels and at this point 
does not change our current science plans or diminish our chances of studying 
key transitions in mineralogy higher on Mount Sharp."

Curiosity is currently examining sand dunes partway up a geological unit 
called the Murray formation. Planned destinations ahead include the hematite-containing 
"Vera Rubin Ridge," a clay-containing geological unit above that ridge, 
and a sulfate-containing unit above the clay unit.

The rover is climbing to sequentially higher and younger layers of lower 
Mount Sharp to investigate how the region's ancient climate changed billions 
of years ago. Clues about environmental conditions are recorded in the 
rock layers. During its first year on Mars, the mission succeeded at its 
main goal by finding that the region once offered environmental conditions 
favorable for microbial life, if Mars has ever hosted life. The conditions 
in long-lived ancient freshwater Martian lake environments included all 
of the key chemical elements needed for life as we know it, plus a chemical 
source of energy that is used by many microbes on Earth.

Through March 20, Curiosity has driven 9.9 miles (16.0 kilometers) since 
the mission's August 2012 landing on Mars. Studying the transition to 
the sulfate unit, the farthest-uphill destination, will require about 
3.7 miles (6 kilometers) or less of additional driving. For the past four 
years, rover drive planners have used enhanced methods of mapping potentially 
hazardous terrains to reduce the pace of damage from sharp, embedded rocks 
along the rover's route.

Each of Curiosity's six wheels is about 20 inches (50 centimeters) in 
diameter and 16 inches (40 centimeters) wide, milled out of solid aluminum. 
The wheels contact ground with a skin that's about half as thick as a 
U.S. dime, except at thicker treads. The grousers are 19 zigzag-shaped 
treads that extend about a quarter inch (three-fourths of a centimeter) 
outward from the skin of each wheel. The grousers bear much of the rover's 
weight and provide most of the traction and ability to traverse over uneven 
terrain.

JPL, a division of Caltech in Pasadena, California, manages NASA's Mars 
Science Laboratory Project for NASA's Science Mission Directorate, Washington, 
and built the project's rover, Curiosity. For more information about the 
mission, visit:

http://mars.jpl.nasa.gov/msl/

News Media Contact
Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278
guy.webster at jpl.nasa.gov

2017-079