Andrew C. Schuerger, Ph.D. Dept. of Plant Pathology, University of Florida

The Harsh Mars Surface Environment may Mitigate The Harsh Mars Surface Environment may Mitigate Against the Forward Contamination of Mars During Against the Forward Contamination of Mars During

Robotic and Human MissionsRobotic and Human Missions

The Harsh Mars Surface Environment may Mitigate The Harsh Mars Surface Environment may Mitigate Against the Forward Contamination of Mars During Against the Forward Contamination of Mars During

Robotic and Human MissionsRobotic and Human Missions

Andrew C. Schuerger, Ph.D.Andrew C. Schuerger, Ph.D.

Dept. of Plant Pathology, University of FloridaDept. of Plant Pathology, University of FloridaSpace Life Sciences Lab, Kennedy Space Center, FLSpace Life Sciences Lab, Kennedy Space Center, FL

Andrew C. Schuerger, Ph.D.Andrew C. Schuerger, Ph.D.

Dept. of Plant Pathology, University of FloridaDept. of Plant Pathology, University of FloridaSpace Life Sciences Lab, Kennedy Space Center, FLSpace Life Sciences Lab, Kennedy Space Center, FL

Environmental parameter Earth Mars

Solar constant 1368 W m-2 590 W m-2

Solar UV irradiation λ ≥ 290 nm λ > 190 nm

UVC + UVB flux at surface ≈ 2 W m-2 8.6 W m-2 (tau = 0.3)0.37 W m-2 (tau = 3.5)

Solar particle events (SPE) none up to 0.1 Sv/h

Galactic cosmic radiation (GCR) 1-2 mSv/yr 0.1-0.2 Sv/yr

Mean atmospheric pressure 1013 mb (105 Pa) 7.1 mb (710 Pa)

Temperature range –50 to 45 oC –90 to –10 oC (Viking data)–90 to +20 oC (S. hemisphere)

Atmosphere 78.1 % N2 95.3 % CO2

20.9 % O2 2.7 % N2

0.0375 % CO2 1.6% Ar

variable % H2O 0.1% O2

UV-Glow discharge from blowing dust minimal effect likely and prevalent

Nightglow [N+ + O– = NO] yields UV minimal effect prevalent

Solar UV-induced volatile reactants [O2

–, O–, H2O2, O3, etc.]minimal effect prevalent

Globally distributed oxidizing soil no prevalent

Adapted from Applebaum and Flood (1990), Buhler and Calle (2003), Cockell and Andrady (1999), Horneck et al. (2001,2003), Kuhn and Atreya (1979), Owen (1992), and Schuerger et al. (2003, 2004).

Microbial Bioload at Launch is Finite: Limited Species Diversity and Biomass.Microbial Bioload at Launch is Finite:

Limited Species Diversity and Biomass.

Spore-formers ≈ 10% total biomass (range: 1-34%; Dillon et al., 1973).

Culturable species are typically human-associated, airborne, and soil borne microbes.

Non-culturable species are present but poorly defined at the moment.

Average bioload launched: 3.0 x 105 spore-formers; + ≈ 1 decade higher non-

spore forming species; + ≈ 2 decades higher non-culturable species.

Spore-formers ≈ 10% total biomass (range: 1-34%; Dillon et al., 1973).

Culturable species are typically human-associated, airborne, and soil borne microbes.

Non-culturable species are present but poorly defined at the moment.

Average bioload launched: 3.0 x 105 spore-formers; + ≈ 1 decade higher non-

spore forming species; + ≈ 2 decades higher non-culturable species.

Effects of Vacuum on Survival of Endospores of Bacillus subtilis.Effects of Vacuum on Survival of Endospores of Bacillus subtilis.

Spirit at Gusev Crater Spirit at Gusev Crater

Mars Electrostatic Chamber (MEC), KSC.Mars Electrostatic Chamber (MEC), KSC.

Schuerger et al., 2003, Icarus 165:253-276. Schuerger et al., 2003, Icarus 165:253-276.

Mars Simulation Chamber (MSC), KSC.Mars Simulation Chamber (MSC), KSC.

Effects of UV dosage on the Survival of Bacillus subtilis HA101 under Mars-Normal UV and Earth-Normal Environmental Conditions.

Effects of UV dosage on the Survival of Bacillus subtilis HA101 under Mars-Normal UV and Earth-Normal Environmental Conditions.

Schuerger, Newcombe, Venkateswaran 2005, Icarus, submitted. Schuerger, Newcombe, Venkateswaran 2005, Icarus, submitted.

Time (minutes)0 0.25 0.5 1 5 15 30 60 120 180

N/N

o

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

*

b

a

d

e e

UVC + UVB (200 - 320 nm) Dosage (kJ m-2) (tau = 0.5)

0 3.20.590.320.15 35.217.68.8 70.4

Time (minutes)0 10 20 30 40 50 60

N/N

o

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

c

100

100

100

100100

100100

5725

Bacillus pumilus SAFR-032

b

e

* 0

105.6

Time (minutes)0 0.25 0.5 1 5 15 30 60 120 180

N/N

o0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

* *

b

a

d

dd


0 3.20.590.320.15 35.217.68.8 70.4

Time (minutes)0 5 10 15 20 25 30

N/N

o

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

c

cd

100

75

100

100

100

1350 1313

Bacillus subtilis HA101

* 0

105.6

Time (minutes)0 0.25 0.5 1 5 15 30 60 120

N/N

o

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

* *

b

a


0 3.20.590.320.15 35.217.68.8 70.4

Time (minutes)0 1 2 3 4 5

N/N

o

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

100

75

100

100

100

013 0 0

Bacillus megaterium KL-197

* *

c

d

e

Rapid inactivation kinetics under equatorial Mars UV simulations.Rapid inactivation kinetics under equatorial Mars UV simulations.

Survival of Bacteria on Sun-Exposed Spacecraft Surfaces. Survival of Bacteria on Sun-Exposed Spacecraft Surfaces.

Lander Pad 3; Viking 1Lander Pad 3; Viking 1

Spirit LanderSpirit Lander

Growth of Seven Bacillus spp. under Martian Conditions.Growth of Seven Bacillus spp. under Martian Conditions.

•Pressure: down to 15 mb•Temp: 30, 20, 15, 10, & 5 C•Gases: CO2 vs ppO2/ppN2

•Pressure: down to 15 mb•Temp: 30, 20, 15, 10, & 5 C•Gases: CO2 vs ppO2/ppN2

•Pressure: down to 0.1 mb•Temp: -100 to +200 C (programmable)•Gases: CO2; O2/N2; Mars mix (top 5 gases)

•UV-VIS-NIR: equatorial to polar fluence rates•Dust loading from tau 0.1 to 3.5

•Pressure: down to 0.1 mb•Temp: -100 to +200 C (programmable)•Gases: CO2; O2/N2; Mars mix (top 5 gases)

•UV-VIS-NIR: equatorial to polar fluence rates•Dust loading from tau 0.1 to 3.5

Effects of Temperature on Growth of Vegetative Cells 7 Bacillus spp.Effects of Temperature on Growth of Vegetative Cells 7 Bacillus spp.

Bacillus species 30 oC 20 oC 15 oC 10 oC 5 oC

B. pumilus (SAFR-032) 4 3 0.95 0 + 0 +

B. pumilus (FO-36B) 4 2.8 0.65 0 + 0 +

B. subtilis (HA-101) 4 2.4 0.5 0 + 0 +

B. subtilis (42HS-1) 4 3 0.45 0 + 0 +

B. megaterium (KL-197) 4 2.8 1.1 0 + 0 +

B. nealsonii (FO-092) 4 1.6 0 + 0 + 0 +

B. licheniformis (KL-196) 4 1.1 0 + 0 + 0 +

Bacillus species 30 oC 20 oC 15 oC 10 oC 5 oC

B. pumilus (SAFR-032) 0.6 0.07 0 + 0 + 0 +

B. pumilus (FO-36B) 0.55 0 + 0 + 0 + 0 +

B. subtilis (HA-101) 1 0.07 0 + 0 + 0 +

B. subtilis (42HS-1) 0.75 0.09 0 + 0 + 0 +

B. megaterium (KL-197) 0.2 0.05 0 + 0 + 0 +

B. nealsonii (FO-092) 1.3 0.09 0 + 0 + 0 +

B. licheniformis (KL-196) 1.4 0.17 0 + 0 + 0 +

Rating scale: 4 = large robust colonies > 5 mm in diameter; 3 = colonies 2-4 mm in diameter; 2 = colonies ≈ 1 mm in diameter; 1 = colonies ≈ 0.5 mm in diameter; 0.50 = colonies < 0.5 mm in diameter; 0.1 = smallest visually discernable growth; 0 = no growth ; 0 = no growth (n = 5).Rating scale: 4 = large robust colonies > 5 mm in diameter; 3 = colonies 2-4 mm in diameter; 2 = colonies ≈ 1 mm in diameter; 1 = colonies ≈ 0.5 mm in diameter; 0.50 = colonies < 0.5 mm in diameter; 0.1 = smallest visually discernable growth; 0 = no growth ; 0 = no growth (n = 5).

O2/N2 atmosphere O2/N2 atmosphere

CO2 atmosphereCO2 atmosphere

48 hrs at 1013 mb48 hrs at 1013 mb

Effects of Pressure on Vegetative Cells of 7 Bacillus spp.Effects of Pressure on Vegetative Cells of 7 Bacillus spp.

O2/N2 atmosphereO2/N2 atmosphere

Bacillus species 1013 mb 100 mb 50 mb 35 mb 25 mb

B. pumilus (SAFR-032) 4 4 2.5 1 0.1

B. pumilus (FO-36B) 4 4 2.5 0.5 0.1

B. subtilis (HA-101) 4 3.5 2.2 1 0.1

B. subtilis (42HS-1) 4 3.2 2.1 0.5 0.1

B. megaterium (KL-197) 4 3 2 0.3 0.1

B. nealsonii (FO-092) 4 3.7 3 1 1

B. licheniformis (KL-196) 4 3.5 3 1 1

CO2 atmosphere CO2 atmosphere


B. pumilus (SAFR-032) 0.6 0.29 0.07 0.17 0.05

B. pumilus (FO-36B) 0.5 0.07 0.05 0.12 0.02

B. subtilis (HA-101) 1 0.9 0.85 0.35 0.2

B. subtilis (42HS-1) 0.55 0.1 0.02 0.2 0.12

B. megaterium (KL-197) 0.6 0.14 0.05 0.2 0

B. nealsonii (FO-092) 1.6 1.7 1.8 1.4 0.75

B. licheniformis (KL-196) 1.3 1.2 1.3 1.2 0.6


48 hrs at 30 C48 hrs at 30 C

Effects of Pressure on Germination and Growth of Endospores 7 Bacillus spp.Effects of Pressure on Germination and Growth of Endospores 7 Bacillus spp.



B. pumilus (SAFR-032) 4 3 1.8 0 + 0 +

B. pumilus (FO-36B) 4 3 1.8 0 + 0 +

B. subtilis (HA-101) 4 3.3 2.3 0.5 0 +

B. subtilis (42HS-1) 4 3 2 0 + 0 +

B. megaterium (KL-197) 4 3.7 2.3 0 + 0 +

B. nealsonii (FO-092) 4 4 3 0 + 0 +

B. licheniformis (KL-196) 4 4 3 0 + 0 +



B. pumilus (SAFR-032) 0 + 0 + 0 + 0 + 0 +

B. pumilus (FO-36B) 0 + 0 + 0 + 0 + 0 +

B. subtilis (HA-101) 0.5 0 + 0 + 0 + 0 +

B. subtilis (42HS-1) 0.03 0 + 0 + 0 + 0 +

B. megaterium (KL-197) 0 + 0 + 0 + 0 + 0 +

B. nealsonii (FO-092) 1.9 1.3 1.3 1 0 +

B. licheniformis (KL-196) 1 1 0.8 0.7 0 +


48 hrs at 30 C48 hrs at 30 C

Effects of Pressure on Growth of 6 Non-Spore Forming Species.Effects of Pressure on Growth of 6 Non-Spore Forming Species.




48 hrs at 30 C48 hrs at 30 CBacteria O2/N2

1013 mb 100 mb 25 mb

Escherichia coli (K12) 3.5 3.0 0 +

Streptomyces coelicolor (A3) 2.8 2.0 0 +

Deinococcus radiodurans (R1) 2.5 2.0 0 +

Acinetobacter caloaceticus (50V1) 3.3 2.0 0 +

Comamonas acidovorans (30V3) 3.5 2.8 0 +

Clavibacter michiganensis (27V1B) 3.5 2.3 0 +

Bacillus subtilis (HA101) 4.0 3.3 0 +

CO2

1013 mb 100 mb 25 mb

Escherichia coli (K12) 1.2 0.9 0.5

Streptomyces coelicolor (A3) 0 + 0 + 0 +

Deinococcus radiodurans (R1) 0 + 0 + 0 +

Acinetobacter caloaceticus (50V1) 0 + 0 + 0 +

Comamonas acidovorans (30V3) 0 + 0 + 0 +

Clavibacter michiganensis (27V1B) 0 + 0 + 0 +

Bacillus subtilis (HA101) 0.6 0.4 0 +

Mars Base-1: 2030+Mars Base-1: 2030+

Courtesy of Carter Emmart.

ConclusionsConclusions

Spacecraft are assembled under strict conditions which constrain bioloads at launch to low numbers of species and low total biomass.

During cruise phase to Mars, spore-forming species are reduced about 1 order of magnitude; non-spore formers likely 2-3 orders of magnitude.

Once on Mars, UV irradiation rapidly reduces bioloads on sun-exposed surfaces by up to 6 orders of magnitude within a few tens of minutes to a few hours.

And for those lucky microbes to survive on UV shielded surfaces, the synergistic effects of low pressure, low temperature, and CO2 atmospheres (+ other biocidal factors) create significant hurdles over which common spacecraft contaminants must cope with for continued survival and growth on Mars.

Spacecraft are assembled under strict conditions which constrain bioloads at launch to low numbers of species and low total biomass.

During cruise phase to Mars, spore-forming species are reduced about 1 order of magnitude; non-spore formers likely 2-3 orders of magnitude.

Once on Mars, UV irradiation rapidly reduces bioloads on sun-exposed surfaces by up to 6 orders of magnitude within a few tens of minutes to a few hours.

And for those lucky microbes to survive on UV shielded surfaces, the synergistic effects of low pressure, low temperature, and CO2 atmospheres (+ other biocidal factors) create significant hurdles over which common spacecraft contaminants must cope with for continued survival and growth on Mars.

Documents

Andrew C. Schuerger, Ph.D. Dept. of Plant Pathology, University of Florida