Chemical elements preliminary mapping
Early Mapping of Hydrogen,
Potassium and Silicon
from the Gamma lines
L. d’Uston, S. Maurice, O. Gasnault
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
1
Chemical elements preliminary mapping
4
3
2
#0
Ge
76
Ge(p,p'n)
132.68
#5
Ge
72
Ge(p,p'n)
194.43
71m
75m
#1
46m
Sc
136.00
#13
67
Ga
70
Ge(p,a)
402.69
#8
Pb
294.18
214
10
6
#6
212
Pb
235.75
8
7
6
5
4
#18
annih
511.00
#14
Na
69m
Zn
(n,ng);spal
438.87
#27
72
Ge
72
Ge(n,n')
~693.00
23
#11
Pb
350.56
214
#40
Ti
48
V
48
Sc
(n,ng)
983.72
48
#19
Ge
70
Ge(p,p'n)
584.02
69
#26
Cu
670.77
#30
Co
(spal)
817.97
Counts per Channel
#21
Bi
608.71
#16
Na
472.24
214
24m
2
#3
As
Ge(p,2n)
181.52
71
72
10
5
8
7
6
5
4
#33
Ge
70
Ge(p,p'n)
882.65
69
#4
Ga
Ge(p,a)
190.39
67
70
69
#45
Ga
70
Ge(n,na)
1048.95
#50
Zn
(Spal)
1124.50
65
#12
43
K
43
Sc
372.29
2
#17
7
Be
(spal)
477.17
#20
Ge
As
(SAW)
~598.00
74
74
4
#22
43
K
617.39
#29
Co
(spal)
811.24
#59
Mn
(Spal)
~1434.30
52m
#54
Na
22
Ne
1274.44
22
#10
Ac
337.10
#15
Mg
450.71
48
44
#38
228
Ac
969.26
23
#55
Ti
48
V
48
Sc
1312.29
#51
Sc
(Spal)
1157.00
66
#35
228
Ac
910.98
228
#9
67
Ga
70
Ge(p,a)
308.91
#48
Ge
70
Ge(p,p'n)
1117.70
#44
Sc
1038.20
48
#28
10
B
719.02
#7
Sc
(spal)
269.56
44m
3
10
#34
Ti
46
Sc
889.55
46
58
65
3
#58
Mg
Al
24
Na
(n,ng)
1368.58
24
#31
72
Ge
(SAW)
~835.50
63
#2
Ga
(spal)
~153.60
#42
Al
1014.65
27
58
#32
27
Al(843.8)
27
Mg(844.01)
56
Fe(846.7)
~843.60
#37
Cu
962.50
63
#60
40
K
1460.78
#52
Co
1173.12
60
#39
Mg
974.81
25
#43
Ar
1021.10
45
#46
Ga
72
Ge(p,na)
1087.00
68
#47
Ge
1107.00
69
#56
Co
1332.94
60
#57
Ge
1346.68
69
8
200
Workshop HEND - 2002
May 20th – 22nd 2002
400
600
800
Energy (keV)
1000
1200
1400keV
2001 Mars Odyssey GRS
2
Chemical elements preliminary mapping
Data sets
Gammas
Raw data from Query Tool (gammaspatial + engineering)
Time selection:
Feb 20 – March 9
before annealing
Temperature selection:


GRS_IS_TEMP_A < -165oC
2 weeks
55,972 spectra (~304 hours)
Neutrons
Press release data from W. Feldman & R. Tokar
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
3
Chemical elements preliminary mapping
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
4
Chemical elements preliminary mapping
0.8
H (2223)
Counts / min / keV
Al (2210)
0.6
North (raw, >+75º)
0.4
South (bkg corrected, < -60º)
0.2
Middle (bkg corrected, > -60º, < +75º)
2100
2150
2200
2250
2300
2350
Energy (keV)
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
5
Chemical elements preliminary mapping
Spectral Analysis
(counts/19.6 sec)
2.0 MeV
Continuum
H-line
2.4 MeV
Background
2.215 – 2.230 MeV
Energy
Energy callibration [W. Boyton, Feb 02]
Slope = 0.6152 keV/channel
Intercept = 18.86 keV
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
6
Chemical elements preliminary mapping
Mapping at 30o resolution (equal area)
(8)
(8)
(12)
(15)
(12)
Min = 530 spectra
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
7
Chemical elements preliminary mapping
Map of background
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
8
Chemical elements preliminary mapping
Background with MOLA
Below –45o
Above +45o
 Effects of atmospheric Absoption
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
9
Chemical elements preliminary mapping
Map of background (corrected for 0 km MOLA altitude)
(same color range)
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
10
Chemical elements preliminary mapping
Map above continuum  H-LINE map
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
11
Chemical elements preliminary mapping
Map of H-line (corrected for 0 km MOLA altitude)
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
12
Chemical elements preliminary mapping
Epithermal neutrons [Press release data]
! Arb. Units = constant - epithermals !
Smooth 4o
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
13
Chemical elements preliminary mapping
Epithermal neutrons: Rebin to 30o
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
14
Chemical elements preliminary mapping
Correlation epithermals/gammas (1)
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
15
Chemical elements preliminary mapping
Correlation epithermals/gammas (2)
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
16
Chemical elements preliminary mapping
Conclusions
•
•
Map of HYDROGEN is feasible; it makes sense…
Map of BACKGROUND:
–
–
•
Correlated with altitude (atmospheric effect)
Corrected map shows signal at poles
Agreement between epithermal neutrons & gamma H-line:
–
–
–
Very good at first order
Strenghten epithermal detection of H
Differences have not been interpreted
Future Developments
•
•
•
•
•
•
Quantify statistical significance per pixel
Increase surface resolution of gamma’s (15o by early May – 8o at poles)
Use better epithermal map
Incorporate HEND data ?
Improve spectral analysis (norm to thermals / line fit…)
Quantify gamma H-line  Quantification of abundances
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
17
Chemical elements preliminary mapping
10.00
9.00
8.00
Counts per Minute
7.00
Mg 1369 keV
6.00
Ti 1382 keV
K 1461 keV
5.00
H 2223 keV
4.00
Si 1779 keV
Fe 7132 keV
3.00
Fe 847 keV
2.00
1.00
0.00
90N_60N 60N_30N 30N_00N 00S_30S 30S_60S 60S_90S
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
18
Chemical elements preliminary mapping
K line (1.461 MeV) underlying continuum versus MOLA altitude
Slope = 0.05 C/dt*km
Offset =4.045 C/dt
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
19
Chemical elements preliminary mapping
Si line (1.779 MeV) underlying continuum versus MOLA altitude
Slope = 0.032C/dt*km
Offset = 2.885C/dt
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
20
Chemical elements preliminary mapping
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
21
Chemical elements preliminary mapping
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
22
Chemical elements preliminary mapping
Atmospheric correction
I(h,E) = I0 exp (-α. g)
Slope  E-1.6
¤ α (E) attenuation
coefficient in cm2/g
¤ g (h) optical
thickness
in g/cm2
Using
ρ(h)= ρ0 exp (-h/10.8)
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
23
Chemical elements preliminary mapping
• Atmospheric transmission:
I(h,E) = I0 exp (-α. g)
g (h) optical thickness in g/cm2
α (E) attenuation coefficient in cm2/g
Workshop HEND - 2002
May 20th – 22nd 2002
2001 Mars Odyssey GRS
24