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ENDPAPER 



cience museums are not 

 always the sedate reposi- 

 tories you stroll through 

 on your tour of their galleries. 

 Exciting research goes on be- 

 hind the scenes, out of sight of 

 visitors. Sometimes even long- 

 held samples from the collec- 

 tions take a star turn in the drama of 

 scientific advance. Recently one of 

 the meteorites in the collection I cu- 

 rate at New York's American Mu- 

 seum of Natural History (AMNH) 

 got to play more than a bit part m 

 the exploration of Mars. 



In mid-January 2005, I got a call 

 from Stephen Gorevan, chairman of 

 Honeybee Robotics, a Manhattan- 

 based company that designed and 

 built a key instrument aboard the 

 Mars rovers, Opportunity and Spirit. 

 Opportunity, Steve told me, had been 

 driving across the surface of Mars 

 when it discovered an iron meteorite 

 near its own heat shield. 



A meteorite on Mars was an excit- 

 ing find. What could Opportunity's 

 earthbound handlers learn about it? 

 Steve warmed to his topic. On the 

 rover's extendable arm is Honeybee's 

 rock abrasion tool, or RAT. It's a so- 

 phisticated grinding machine that 

 sweeps the ubiquitous red Martian 

 dust off rocks, grinds away the surfice 

 coating to get to the fresh rock un- 

 derneath, and then brushes away the 

 cuttings. Other instruments on the 

 arm measure the rock composition 

 before and after "ratting." 



But the KAT had never been test- 

 ed on an iron meteorite. So Steve's 

 question was simple. Would the 

 grinding bit survive? 



Iron meteorites are much, much 

 harder than basalt, the predominant 

 kind of rock the rovers had been en- 

 countering. In fact, until the invention 



Stunt Double 



By Denton S. Ebel 



Above: Test grinding of the Santa Rosa 

 meteorite left a nearly circular hole 46 

 millimeters across and less than a millimeter 

 deep. Below: Artist's conception of the Mars 

 rover Opportunity, sampling an iron mete- 

 orite on the Martian surface. 



of Steel, meteoritic iron was the hard- 

 est malleable material available to tool- 

 makers. The grinding bit on the RAT 

 is made of diamond fragments embed- 

 ded in hard resin. The diamond, of 

 course, is harder than an iron mete- 

 orite, but Opportunity's RAT had al- 

 ready done twenty-two grinds. Al- 

 though the bit still seemed in good 

 condition, no one wanted to wear it 

 out with one shot on a meteorite. 



Steve continued: Could Honeybee's 

 lab test a duplicate RAT on a mete- 

 orite from the collection at AMNH? 

 Without hesitation, I said, Yes! 



Our collections exist to advance 

 knowledge of the natural world. 

 Helping to study the first meteorite 



ever found on another planet 

 certainly fit that mission. Our 

 sample was needed to help 

 Steven Squyres, the principal 

 investigator for the rovers, 

 make a scientific decision 

 critical to one of the most 

 productive NASA missions 

 ever. Here was an opportunity (no 

 pun intended) to complement and 

 support extraterrestrial field research 

 with a laboratory experiment, made 

 possible by AMNH's collection. 



We needed a large piece of me- 

 teorite with a flattish surface, 

 because the head of the RAT had to 

 rest against its target. I ultimately 

 chose one of our samples of the San- 

 ta Rosa meteorite, discovered in 

 Colombia in 1810. 



Tvk'o Honeybee engineers, Philip 

 Chu and Alastair Kusack, tested a 

 RAT on both cut and natural faces 

 of the Santa Rosa sample, in a cham- 

 ber that reproduced Martian air com- 

 position, pressure, and temperature. 

 Their results shov/ed that grinding 

 Santa Rosa wore down the bit on the 

 KAT extremely fast. My advice was: 

 "Don't risk it. We're there to study 

 Mars, not iron meteorites." 



And that's what Squyres decided. 

 Opportunity carried out some more 

 investigations of the surface of the 

 meteorite, then moved on. Santa 

 Rosa is safely back at AMNH, along 

 with a vial of particles recovered 

 from the grinding. It bears only a 

 shallow scar: a reminder that it 

 served our mission with strength 

 and stubborn resolve. 



Dentos S. Ebel is a ciiraior in the 

 dcpartuiciit of earth and planetary sciences at 

 the American Mnsetini of Natnral History in 

 New York City 



