Space Weather & the Radiation Environment at Mars: Energetic Particle Measurements with MSL RAD

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1 Space Weather & the Radiation Environment at Mars: Energetic Particle Measurements with MSL RAD Donald M. Hassler Southwest Research Institute, Boulder, CO & Institut d Astrophysique Spatiale, Orsay, France R.F. Wimmer-Schweingruber (CAU/Kiel), C. Zeitlin (NASA/JSC) B. Ehresmann (SwRI) and the MSL RAD Team Artist s Concept. NASA/JPL-Caltech

2 The Radiation Assessment Detector (RAD) Overview MSL RAD is a working Asset on the Surface of Mars characterizing the changing Radiation Environment on Mars over the Solar Cycle, due to Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) originating from CMEs & Solar Flares. Mass = 1.56 kg Power = 4.2 W RAD 2

3 Space Weather on Mars The surface of Mars is much more exposed to space radiation than is the surface of Earth, for two reasons: Mars lacks a planetary magnetic field (magnetosphere) Mars atmosphere is much thinner ~1% of thickness of Earth s atmosphere

4 Secondary Particle Production from Galactic Cosmic Rays Why we need to make Ground-Truth Measurements to validate our models!

5 Astronaut Safety Requires Measuring ALL of the Important Energetic Particles Heavy ions contribute disproportionately to the radiation dose rate for humans (called Dose Equivalent), which is the radiation which affects astronauts and other life (Wilson et al., 1997).

6 The RAD Instrument (Overview) First Radiation Measurements on the Surface of Mars RAD consists of a combined: Charged Particle and Neutral Particle analyzer Mass = 1.56 kg Power = 4.2 W RAD is comprised of: Solid state detector telescope and CsI calorimeter with active coincidence logic to identify charged particles. Separate scintillators w/ anti-coincidence logic to detect neutrons and g-rays.

7 RAD Measurement Capability (Overview) Charge particles (protons and heavy ions up to Fe) (1 Z 26) vs energy & time Neutral particles (neutrons and γ-rays) (1-100 MeV neutrons) vs energy and time Absorbed Dose and Dose rate (LET of 0.3 to 1000 kev/mm) as a function of time Dose Equivalent (timeresolved Si LET spectra to determine LET-based Quality Factors) /n

8 RAD Observations (Inside the MSL Spacecraft) During Cruise On its way to Mars, inside the MSL Spacecraft, RAD served as a proxy to help validate models of the radiation levels expected inside a spacecraft that future astronauts may experience MSL Spacecraft during Cruise Manned Crew Exploration Vehicle (Orion)

9 During Cruise: magnetically well connected with Earth Earth MSL Mars

10 MSL RAD Measurements during the cruise GCR Average dose rate: 480 ± 80 ugy/day Dose equivalent rate: 1.84 ± 0.30 msv/day Zeitlin et al 2013, Science

11 RAD Saw Several Large SEP Events during Cruise Flare & SEP Event on March 7, 2012 Courtesy Tim Howard (SwRI)

12 RAD & GOES 13 Observations of the SEP Event on March 7, 2012 GOES Satellite (Earth Orbit) RAD (Inside MSL Spacecraft)

13 Particle Flux (protons/cm 2 /s/sr) Particle Flux (protons/cm 2 /s/sr) MSL Spacecraft Provided Shielding to Solar Energetic Particle Events Day (March 2012) The MSL spacecraft structure (backshell, heatshield, etc.) provides significant shielding from the deep space radiation environment, reducing significantly the particle flux observed by RAD. Particle flux observed by RAD is several orders of magnitude less than that observed by the SIS instrument on ACE. 13

14 SEP Events Contribute to Total Dose During Cruise Time Period (2012) Integrated Dose Equivalent (msv) Total Jan SEP 4.0 Total March 7-15 SEP 19.5 Total May SEP 1.2 SEP Events Total 24.7 GCR average per day 1.84 TOTAL (GCR + SEP) (253 days) 490 During Cruise, SEP Events contributed ~5% to the Total Integrated Dose Equivalent. However, SEP Fluences & Energy Spectra ( Hardness ) are highly variable a very large SEP Event or Super-Event (similar to the 1972 SEP event) could potentially contribute substantially more (>order of magnitude) to the total integrated Dose Equivalent.

15 On the Surface of Mars 100 Years after the Discovery of Cosmic Rays on Earth August 7, 1912 Exactly 100 years after Victor Hess discovered Cosmic Rays from his balloon in Eastern Germany RAD makes the first observations of the radiation environment on the surface of another planet! Credit: Foray (New York Times)

16 NASA/JPL- Caltech/MSSS RAD s new Home: Mastcam image of Mount Sharp s Canyons and Buttes

17 RAD Dose Rate Measurements on the Martian Surface GCR Average dose rate: 210 ± 40 ugy/day Dose equivalent rate: 0.64 ± 0.12 msv/day

18 SEP Events Seen by RAD, GOES & STEREO-B (11 April 2013) Mars/RAD Earth/GOES STEREO-B

19 First SEP Event Observed from the Surface of Mars (11 April 2013) First SEP Event seen on the Surface of Mars!!! STEREO-B RAD GOES-13

20 Solar Events on the Surface of Mars Three one-sol spectra of SEP events (Apr 2013, Oct 2013, Jan 2014)

21 Summary: RAD total Dose Rate during cruise & on the surface thru Sol 1000 During Cruise several medium size SPEs observed On the Surface only small SPEs observed so far...

22 Radiation Environment Summary (after RTG subtraction) RAD Measurement Cruise Mars Surface Charged Particle Flux particles cm -2 s -1 sr -1 Fluence (A2*B) cm -2 s -1 Dose Rate 464 +/ /- 50 mgy/day Avg. Quality Factor <Q> 4.1 +/ /- 0.3 (dimensionless) Dose Equivalent Rate / / msv/day Representative Radiation Dose Rates in Other Environments Natural Bkg Radiation (Earth) ~0.01 msv/day DOE Limit for Radiation Workers ~0.14 msv/day International Space Station (ISS) msv/day

23 Radiation Levels Measured by RAD compared with Common Sources

24 Implication for Manned Mission to Mars: NASA Design Reference Mission Mission Phase Astronaut Career Limit* Dose Equivalent ~1 Sv Notes Depends on age, gender, etc. Cruise to Mars (180 days) ~340 msv near SolarMax Mars Surface Mission (600 days) Mars Surface Mission (450 days) ~420 msv ~315 msv Return to Earth (180 days) ~340 msv near SolarMax Total Mission Dose Equivalent (450 days on Mars) ~1.02 Sv 450 days Total Mission Dose Equivalent (600 days on Mars) ~1.1 Sv 600 days

25 Comparing RAD Observations on Mars with Radiation Transport Models Daniel Matthiae (DLR)

26 Comparing RAD Data with Models: Proton, deuteron, trition, 3 He, 4 He Matthiae et al, 2015 Zenith angle 30 MSL-RAD data: Ehresmann et al GEANT4, PHITS, OLTARIS2013, HZETRN/OLTARIS

27 Comparing RAD Data with Models: Li/Be/B, C/N/O, Z=9-13, Z=14-24, Z 25 Matthiae et al, 2015 Zenith angle 30 MSL-RAD data: Ehresmann et al GEANT4, PHITS, OLTARIS2013, HZETRN/OLTARIS Li/Be/B: PHITS underestimates C/N/O, Z=9-13: agreement reasonable Z=14-24: G4 good, PHITS, HZETRN and OLTARIS2013 overestimate Z>24: all underestimate

28 Comparing RAD Data with Models: Neutrons & Photons Matthiae et al., 2015 MSL-RAD data: Köhler et al Neutrons (GEANT4, PHITS, HZETRN, OLTARIS2013) Good agreement above 1GeV Lower neutron fluxes from OLTARIS2013 below 1GeV (upward fluxes are missing) Photons: Good agreement G4/PHITS HZETRN significantly lower (higher) at energies < 10MeV (>1GeV)

29 MSL/RAD Radiation Transport Modeling Workshop Upcoming Workshop to bring the radiation transport modeling community together to compare their models with each other & with data from MSL/RAD and elsewhere When: Week of May 23-27, 2016 Where: Boulder, Colorado Stay tuned for more information Sponsored by NASA/JSC SRAG, RadWorks & NASA Advanced Exploration Systems Division (AES)

30 What might we expect from an Extreme SPE, Carrington Event or Super-Storm?

31 What should we expect from historically large SPEs or GLEs on Mars Wilson et al., 1997

32 56 e e e, 1956 Feb E Jul E May 04 SEP 8 Event 8.156E+05 Exposure Estimates from Date 1960 Sep E Nov Selected GLEs 7.540E+08 (Kim et al., AGU, ) Nov E Nov E Probabilistic Forecast of Solar Particle Fluence for Mission Durations and Exposure Assessment in Consideration of Integral Proton Fluence at High Energies 1961 Jul E Jan E Nov E Mar E during Extra Vehicular Activity and Inside 5 g/cm Myung-Hee Y. Kim 1, Allan J. Tylka 2, William F. Dietrich 2,3, and Aluminum Francis A. Cucinotta Jan E Sep E Aug E+15 Band Fit Parameters BFO dose, mgy-eq NASA E, msv Date Aug 07 Official 25 No. J0, 6.340E+06 p/cm Consultant R (GV) EVA g/cm Al EVA g/cm Al Feb Apr E E during Extra Vehicular Activity and Inside 5 g/cm Aluminum Apr Jul E E May Sep E E Sep E E+08 Band Fit Parameters BFO dose, mgy-eq NASA E, msv Date Nov Official No. J0, 3.020E E+08 p/cm R0 (GV) EVA g/cm Al EVA g/cm SPEonset date 2 Al May Feb Nov E E E Propensity of SPEs: Hazard Function of Sep Nov Jul E E E Offset Distribution Density Function May Jul E E E Sep Oct Jan E E E p q K ( p q) t t Nov E E E ( t) ( p) ( q) Nov Dec Mar E E E ( t ) Nov Feb Jan E E E Sep Jul E E Aug Date E E Nov Sep Aug E E E Sep Mar Apr E E E Jan Oct Apr a E E E Sep Oct b E E E Aug Sep Oct E E E Aug Nov Oct Date E E E rch Association, Division of Space Life Sciences, SK/SRPE/B37, 2101 NASA Parkway, Houston, TX 77058, USA my 2 Space Science Division, Naval Research Laboratory, Washington, DC 20375, USA allan.tylka@nrl.navy.mil ASA Johnson Space Center, SK/B37, 2101 NASA Parkway Houston, TX 77058, USA francis.a.cucinotta@nasa.go, 1/1957 2/1/1960 2/1/1958 2/1/1960 2/1/1963 2/1/1962 2/1/1966 2/1/1969 2/1/1964 2/1/1966 2/1/1968 2/1/1970 2/1/1972 2/1/1972 2/1/1975 2/1/1974 2/1/1976 2/1/1978 2/1/1978 2/1/1981 2/1/1980 2/1/1982 2/1/1984 2/1/1984 2/1/1987 2/1/1986 2/1/1988 2/1/1990 2/1/1990 2/1/1993 2/1/1992 2/1/1994 2/1/1996 2/1/1996 Probabilistic Forecast of Solar Particle Fluence for Mission Durations 2/1/1999 2/1/1998 2/1/2002 2/1/2005 2/1/2000 2/1/2002 2/1/2004 2/1/2006 (t) 30, protonscm -2 1.E+11 1.E+10 1.E+09 1.E+08 1.E+07 1.E+06 1.E+05 1.E E+11 E E 95 percentile 90 60, protonscm -2 cm -2 1.E+10 1.E+09 1.E+08 1.E+07 1.E+06 1.E+05 1.E E+11 1.E+10 1.E

33 Dose Equivalent (msv) Comparison of Total Radiation Dose Equivalent measured by RAD to modeled Historic SPE Events No significant SPEs to date Contribution of SPEs to Total Dose Eq. (msv) (behind 5 g/cm2 Al shielding) RAD Measurements (to date) Historical SPE Events (Modeled) *SPE Dose Equivalent values modeled behind 5 g/cm2 Aluminum by M.-H. Kim, F. Cucinotta, et al. (AGU, 2012). 400 RAD cruise measurements from Jan-July Nov. 60 SPE includes contributions from 2 events RAD Cruise GCR (6 mo) RAD Cruise SPEs (total) RAD Mars SPEs Feb 1956 SPE July 1959 SPE Nov 1960 SPE Aug 1972 SPE Oct 1989 SPE Oct. 89 SPE includes contributions from 5 events over 1 month.

34 Prospects for the Next Solar Cycle

35 Descending Phase of Cycle 24 more events to come?

36 Large Solar Particle Events are seen throughout the Solar Cycle Histogram of large SPEs (green bars) vs time. Large events are seen throughout the solar cycle.

37 However, predicting the Solar Cycle is difficult! Cycle 23 Data Predictions Actual Cycle 24 Deepest minimum of Space Age in 2009, not predicted. Cycle 24 maximum occurred late & is weakest in over 100 years, not predicted.

38 NSO (National Solar Observatory) Solar Cycle Prediction Sunspot Formation Fraction from Kitt Peak Sunspot Magnetic Field Measurements (Penn et al. 2013) MSFC Cycle 24 Sunspot Number Prediction (Hathaway et al. 2013)

39 Extreme Conditions throughout the Solar Cycle Extreme variations in the past 2 solar cycles have shown that current models clearly lack sufficient predictive capability. If cycle 24 minimum is as deep as 23 s, GCR dose rate will approach worst-case conditions for human expeditions. How bad can it get? We don t really know. We need to characterize these Extreme Conditions 1) Extreme Cycle variations (solar min, solar max) 2) Extreme SPEs (X-Class flares, GLEs, Super-Events )

40 Extended Mission Plan for MSL RAD 1) Characterization of the radiation environment at SOLAR MINIMUM. RAD has ONLY made measurements during Solar Maximum. Current predictions are for Solar Min to occur between ) Characterization of Extreme Solar Particle Events (SPEs). So far on the surface, RAD has only observed small SPEs. Large SPEs can occur well outside solar maximum. 3) MSL and RAD continue to be healthy and operate nominally on the surface of Mars. These data will continue to be useful for both research and operations through the next solar minimum to address these needs.

41 Take-Away Points Observations from RAD on Mars provide additional heliospheric data points to help us improve our understanding & modeling of the 3-D structure of the heliosphere, & the propagation of CMEs & SPEs For a SEP event to make it to the Mars surface, it needs to be relatively hard (high energy) event otherwise the only observed effect is a Forbush decrease We have not yet observed a large SPE from the surface of Mars, but the current solar cycle is proving to be very unpredictable stay tuned! Space Weather Monitoring: As human exploration extends out into the heliosphere and Mars, we will need to provide independent space weather monitoring at the astronaut s location (i.e. since Mars is on the far side of the Sun from Earth 50% of the time )

42 Mahalo! RAD Acknowledgements RAD is supported by NASA (HEOMD/AES) under JPL subcontract # to SwRI....and by DLR in Germany under contract with Christian-Albrechts- Universitat (CAU). 42