9.5.3 SAM on Mars
The SAM experiment has been highly successful. SAM has measured the composition of past and present Martian air and monitored it over time. It has successfully measured isotopes of even the rarest noble gas, xenon. It has detected low-molecular-weight organic compounds of Martian origin. It has detected methane and observed rapid changes in atmospheric methane abundance. SAM has been used for an experiment never before conducted in space, to perform potassium-argon dating to measure the ages of drilled rocks. Even the problem of the MTBSTFA contamination has been turned into a benefit, with the performance of long-term derivatization experiments.
The complexity of SAM experiments and the amount of power they require drive a lot of the supratactical planning on Curiosity. A typical evolved-gas analysis can take three sols (one for preconditioning, one for sample preparation and delivery, and one for heating and evolved gas analysis). The evolved gas analysis usually takes 4 to 6 hours to run to completion, depending on the selected options, and it can leave the rover with a relatively low state of battery charge. For that reason it is common to conduct SAM experiments over weekends and use one weekend sol to recharge batteries.
As of the time of Curiosity’s second extended mission proposal in January 2016, SAM had 75% of its helium supply left, but the pumps were nearing their design lifetime. Duplicates of the pumps on Earth have been tested to survive twice their design lifetime. So, barring any unforeseen events, SAM should have considerable life left. The SAM team is carefully rationing use of the pumps to ensure that they will still be working when the rover reaches the clay-rich layers beyond Vera Rubin Ridge. Usage of the cups and experiments run to date are summarized in Figure 9.24 and Table 9.6, respectively.
Figure 9.24. Schematic diagram of the SAM sample carousel, showing the locations of the numbered cups of different types, and which ones have been used as of sol 1800. For the identities of samples in each used cup, refer to Table 9.6 . Data courtesy Charles Malespin.
Table 9.6. Summary of the SAM solid sample experiments.
Type of run
Sample
Sol #
Cup #
GC Hydrocarbon temp cut(°C)
GCMS
Blank (Rocknest)
88
15
145 - 529
GCMS
Rocknest
93
15
145 - 529
GCMS
Rocknest
96
13
97 - 422
GCMS
Rocknest
99
11
529 - 816
GCMS
Rocknest
171
7
242 - 383
GCMS
Blank (John Klein)
177
23
311 - 816
GCMS
John Klein
196
23
311 - 816
GCMS
John Klein
199
25
242 - 639
GCMS
John Klein
224
27
242 - 639
GCMS
John Klein
227
29
570 - 792
GCMS
Blank (Cumberland)
276
33
442 - 569
GCMS
Cumberland
281
33
442 - 569
GCMS
Cumberland
286
35
571 - 792
GCMS
Cumberland
290
39
226 - 347
NG geochronology
Cumberland
353
41
n/a
GCMS
Cumberland
367
51
226 - 347
GCMS
Cumberland
381
45
226 - 347
GCMS
Cumberland
394
45
226 - 347
NG geochronology
Blank (Cumberland)
408
47
n/a
GCMS
Cumberland
415
47
247 - 620
GCMS
Blank (Cumberland)
421
31
247 - 620
NG geochronology
Blank (Cumberland)
428
53
n/a
GCMS
Blank (Windjana)
602
10
20 - max
GCMS
Windjana
624
10
20 - max
NG geochronology
Windjana
653
12
n/a
NG geochronology
Windjana reheat
685
12
n/a
NG geochronology
Windjana doggy bag
763
14
n/a
GCMS
Blank (Confidence Hills)
769
60
386 - max
GCMS
Confidence Hills
773
60
386 - max
GCMS
Cumberland doggy bag (opportunistic derivatization)
822
51
20 - max
GCMS
Cumberland doggy bag (opportunistic derivatization)
823
51
20 - max
GCMS
GC clean
835
51
n/a
GCMS
Blank (Cumberland)
837
45
20 - 550
GCMS
Blank (Cumberland)
839
45
20 - max
GCMS
Mojave
887
62
200 - max
EGA
Telegraph Peak
928
66
n/a
GCMS
GC clean
981
n/a
n/a
GCMS
GC clean
998
n/a
n/a
GCMS
GC clean
1071
n/a
n/a
GCMS
Buckskin
1076
24
150 - 300, 450 - 550, 650 - max
GCMS
GC clean
1117
n/a
n/a
EGA
Big Sky
1130
26
n/a
EGA
Greenhorn
1147
26
n/a
GCMS
Blank (Greenhorn)
1171
68
560 - 713, 780 - 830
GCMS
Greenhorn
1178
68
376 - 562, 714 - 921
EGA
Gobabeb <150um
1224
28
n/a
EGA
Gobabeb >150um
1237
30
n/a
GCMS
GC clean
1246
n/a
n/a
GCMS
Calibration cup
1286
20
n/a
EGA
Oudam
1382
22
n/a
NG geochronology
Mojave stepped heating part 1
1402
64
n/a
NG geochronology
Mojave stepped heating part 2
1403
64
n/a
NG geochronology
Mojave doggy bag stepped heating part 1
1429
62
n/a
NG geochronology
Mojave doggy bag stepped heating part 2
1430
62
n/a
EGA
Marimba
1443
32
n/a
GCMS
GC clean
1539
n/a
n/a
GCMS
Cumberland doggy bag (opportunistic derivatization)
1543
39
20 - 500
GCMS
Cumberland doggy bag (opportunistic derivatization)
1546
39
20 - max
GCMS
GC clean
1580
n/a
n/a
Doggy bag
Oudam
–
22
n/a
Doggy bag
Marimba
–
32
n/a
Doggy bag
Cumberland
–
33
n/a
Doggy bag
Quela
–
62
n/a
Doggy bag
Quela
–
64
n/a
Doggy bag
Telegraph Peak
–
66
n/a
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Footnotes
1Two papers published before the mission described ChemCam: Maurice et al. (2012) and Wiens et al. (2012)
2Peret et al. (2016)
3Roger Wiens, personal communication, email dated March 14, 2016
The Design and Engineering of Curiosity Page 40
