Slide - 1

LEAG - 2012

SEARCHING FOR WATER ICE PERMAFROST: LEND RESULTS FOR ABOUT THREE YEARS OF OBSERVATIONS

Anton Sanin, Igor Mitrofanov and LEND Team

Slide - 2

LEAG - 2012

Physical basis of the neutron method of studying the prevalence of water

Epithermal neutrondetector

Neutron energy spectrum

Moderation

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LEAG - 2012

+H2OзамедлениеModeration

Physical basis of the neutron method of studying the prevalence of water

Epithermal neutrondetector

Neutron energy spectrum

Slide - 4

LEAG - 2012

More than 50 years ago, it was suggested that some areas near the lunar poles are sufficiently cold to trap and preserve for a very long time (~Gy) hydrogen bearing volatiles, either primordial or produced at the Moon via solar wind interactions or brought to the Moon as water ice by comets and meteoroids.

Slide - 5

LEAG - 2012

LEND omni-directions Epithermal LPNS Epithermal

Maps of epithermal neutrons for north lunar pole

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LEAG - 2012

LEND omni-directions Epithermal LPNS Epithermal

Maps of epithermal neutrons for south lunar pole

Slide - 7

LEAG - 2012

TASK I (PSRs): To test the hypothesis that water ice deposits exist in cold traps of Permanently Shadowed Regions (PSRs)

Experimental results from LPNS pointed out on the Extended Neutron Suppression

Regions at lunar poles

The original TASK for LEND was to resolve the spots of water ice in PSRs in the

Extended Neutron Suppression Regions

pole pole

BACKGROUND, as a cold regolith with

enhanced content of Habout 100 ppm SIGNALS, as PSRs

with water ice

Model with strong suppression in PSRs

Slide - 8

LEAG - 2012

PSR

60° - 70°reference

latitude belt

LEND

Extended polar

suppression of

epithermal

neutrons

poleto equator to equator

Latitude

SIGNAL from a testing PSR

BACKGROUND is the Extended Neutron Suppression Region

TASK I (PSRs): Null hypothesis is tested with a priori no SIGNAL at PSRs over the BACKGROUND (Δ=0)

PSR contour from LOLA

Tota

l n

eu

tro

n c

ou

nt

rate

Δ

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LEAG - 2012

LEND lunar polar maps of collimated epithermal neutrons

North South16.09.2009 – 11.12.2011 02.07.2009 – 01.07.2012

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LEAG - 2012

First method of background subtraction: usage of smooth fit of latitudinal dependence of CSETNs counting rate

Average counting rate vs 2° lat. belts Average counting rate vs 2° lat. belts

This is used for determination of Local suppression #1

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LEAG - 2012

Lunar relief is shown from LOLA altimetry

Second method of background subtraction: usage of CSETNs maps smooth with uniform Gaussian filter with scale

~227 km = 7.5º

This is used for determination of Local suppression #2

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LEAG - 2012

The local neutron suppression parameter is presented in % according to the expression:

where 1.7 is the averaged counting rate in the FOV of LEND collimated detectors outside of extended polar suppression. The value of suppression is proportional to difference Δ between the average counting rate estimated for the PSR and the counting rate measured for the surrounding sunlit areas at same latitude.

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LEAG - 2012

RESULTS of testing SIGNAL (local suppressions) at PSRs: list of largest cases

Name of Crater contained PSR or nearest crater

PSR area, km2

Exposure, secMin Lon,

degMax Lon,

degMin Lat,

degMax Lat,

degLocal

suppression #1Local

suppression #2

Shoemaker 1080.0 30206.1 27.0 63.5 -88.6 -87.4 -3.8% ± 0.9% -8.6% ± 0.9%

Haworth 1019.2 24363.3 -17.3 12.5 -88.1 -86.9 -2.7% ± 1.1% ±-7.2% 1.1%

Faustini 665.2 7978.1 74.1 94.2 -87.6 -86.7 -5.0% ± 1.7% -8.8% ± 1.7%

Sverdrup 550.5 17443.5 -161.0 -123.0 -88.6 -87.8 0.1% ± 1.2% -4.6% ± 1.2%

Amundsen 405.2 1440.8 87.0 95.3 -83.8 -83.0 0.7% ± 4.2% -2.4% ± 4.2%

Rozhdestvenskiy U 390.7 2087.1 148.3 158.1 84.2 85.0 -9.7% ± 3.1% -12.1% ± 3.0%

Cabeus B 382.3 1671.9 -57.4 -51.9 -82.0 -81.3 7.6% ± 3.8% 5.5% ± 3.7%

Lovelace 339.3 1034.3 -112.7 -107.4 81.1 81.8 -1.6% ± 4.7% -2.9% ± 4.7%

Idel'son L 325.9 1713.7 115.2 121.9 -84.2 -83.5 -1.1% ± 3.2% -4.7% ± 3.2%

Sylvester 320.7 523.0 -84.4 -78.6 81.7 82.2 8.1% ± 5.8% 6.2% ± 5.7%

Malapert C (PSR is out of the crater) 306.9 1545.8 8.5 13.4 -82.5 -81.7

2.8% ± 5.7% -3.8% ± 4.1%

Cabeus 283.1 2014.7 -50.4 -42.6 -84.7 -84.1 -13.0% ± 3.2% -15.3% ± 3.2%

Lenard 281.4 1166.7 -113.1 -104.4 84.4 85.1 -3.4% ± 4.0% -6.2% ± 4.1%

de Gerlache 242.5 3132.1 -179.2 179.3 -89.9 -89.4 -0.2% ± 2.4% -3.8% ± 2.4%

Rozhdestvenskiy K 242.5 3488.4 -101.4 -78.0 -88.6 -88.0 -0.2% ± 2.7% -4.7% ± 2.7%

Nansen F 241.2 683.1 -148.2 -143.5 81.3 82.1 -9.5% ± 5.6% -11.2% ± 5.6%

Haworth (PSR is out of the crater) 225.3 1037.1 59.0 66.3 83.9 84.6

6.0% ± 4.8% 3.1% ± 4.7%

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LEAG - 2012

CONCLUSIONS for the TASK I (PSRs):

1. Some large PSRs have enhancement of Hydrogen about 200 – 500 ppm (average in depth) in comparison with their sunlit surrounding. Shoemaker and Cabeus are the best candidates for PSRs with water ice. Water in Cabeus was confirmed by observations by LCROSS

2. There is no statistically significant difference of neutron suppressions for most of largest PSRs in comparison with their local sunlit vicinity.

Based on these results, LEND has focused on another TASK II (NSRs):

To TEST local NEUTRON SUPPRESSION REGIONS (NSRs) based only on the LEND neutron mapping data without any a priory information or hypotheses.

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LEAG - 2012

NSR

60° - 70°reference

latitude belt

LEND

Extended polar

suppression of

epithermal

neutrons

poleto equator to equator

Latitude

SIGNAL from a testing NSR

BACKGROUND is the Extended Neutron Suppression Region

Tota

l n

eu

tro

n c

ou

nts

ra

te

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LEAG - 2012

NSRs were found, as statistically significant decreases of epithermal neutronemission by 2.5% and 5.0% from the level of Extended Suppression

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LEAG - 2012

Testing detected Neutron Suppression Regions (NSRs) by local temperature effect

Cabeus Shoemaker

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LEAG - 2012

CONCLUSIONS for the TASK II (NSRs):

1. Several local NSRs are found, which have enhancement of Hydrogen about 200 –500 ppm (average in depth) in comparison with their surrounding. Some of them includes PSR (the case of Shoemaker – NSR S1), some overlaps with PSRs (the case of Cabeus – NSR S4), some lies outside of PSR (the case of Malapert – NSR S3)

2. The simple mechanism of cold traps in PSRs does not work for NSRs, and some more sophisticated physical model is necessary to explain them:

- water from comets? - water from solar wind? - other?

Slide - 19

LEAG - 2012

Extended mission