The Photochemistry of Unprotected DNA and DNA inside Bacillus subtilis Spores Exposed to Simulated Martian Surface Conditions of Atmospheric Composition, Temperature, Pressure, and Solar Radiation

Solar radiation may be shielded by the terrain relief before reaching the Martian surface, especially over some rugged terrains. Yet, to date, no comprehensive studies on the spatial structure of shielded astronomical solar radiation (SASR) and the possible sunshine duration (PSD) on Mars have been conducted by previous researchers. Previous studies generally ignored the influences of the terrain on the SASR and PSD, which resulted in a corresponding unexplored field on SASR. The purpose of this paper is to study the Martian spatial-temporal structure of SASR and the PSD under terrain influences. In this paper, the theory of Earth’s SASR, the previous Martian SASR model and the theory of planetary science were combined to propose the SASR model that can be applied to Mars. Then, with the spectrum method theory of geography, we defined two new concepts of spectrums to explore the spatial-temporal distribution of SASR and PSD in different Martian landforms. We found SASR and PSD on Mars were significantly influenced by terrain relief and latitude and showed sufficient regularity, which can be concluded as a gradual attenuation with terrain relief and a regularity of latitude anisotropy. The latitude anisotropy feature is a manifestation of the terrain shielding effect. With the latitude varying, SASR and PSD at different temporal scale generally showed different features with those of Earth, which may be attributed to the imbalanced seasons caused by Martian moving orbits and velocity. Compared to PSD, SASR showed more regular variation under terrain relief and was more influenced by the terrain relief which revealed that SASR is more sensitive to terrain relief than PSD. Additionally, the critical area is a quantitative index to reflect the stable spatial structure of SASR and PSD in different landforms and may be viewed as the minimum test region of sample areas. The corresponding result of the experiments herein indicated that either spectrum can effectively depict the spatial-temporal distribution of SASR and PSD on Mars under terrain relief and deepen the understanding of the variation of SASR and PSD influences by terrain. The critical area of either spectrum can be employed to explore and determine the stable spatial structure of SASR and PSD in different landforms. The proposed Martian SASR model and the new spectral method theory shed new light on revealing the spatial-temporal structure of SASR and PSD under terrain influences on Mars.

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Solar radiation incident on the Martian surface

Journal of Molecular Evolution ◽

10.1007/bf01732367 ◽

1979 ◽

Vol 14 (1-3) ◽

pp. 57-64 ◽

Cited By ~ 89

Author(s):

W. R. Kuhn ◽

S. K. Atreya

Keyword(s):

Solar Radiation ◽

Martian Surface ◽

Radiation Incident ◽

Solar Radiation Incident

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Extended survival of several organisms and amino acids under simulated martian surface conditions

Icarus ◽

10.1016/j.icarus.2010.11.011 ◽

2011 ◽

Vol 211 (2) ◽

pp. 1162-1178 ◽

Cited By ~ 30

Author(s):

A.P. Johnson ◽

L.M. Pratt ◽

T. Vishnivetskaya ◽

S. Pfiffner ◽

R.A. Bryan ◽

...

Keyword(s):

Amino Acids ◽

Martian Surface ◽

Surface Conditions ◽

Extended Survival

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The dramatic retreat of Mount Kenya’s glaciers between 1963 and 1987: greenhouse forcing

Annals of Glaciology ◽

10.1017/s0260305500004924 ◽

1992 ◽

Vol 16 ◽

pp. 127-133 ◽

Cited By ~ 74

Author(s):

Stefan Hastenrath ◽

Phillip D. Kruss

Keyword(s):

Heat Transfer ◽

Solar Radiation ◽

Latent Heat ◽

Greenhouse Effect ◽

Longwave Radiation ◽

Atmospheric Composition ◽

Specific Humidity ◽

Sensitivity Analyses ◽

Sensible Heat ◽

Indirect Forcing

The retreat of the glaciers on Mount Kenya is quantitatively well documented for the intervals 1899–1963 and 1963–1987. The ice recession between 1899 and 1963 was strongly dependent on solar radiation geometry. By contrast, the ice thinning between 1963 and 1987 amounted to about 15 m for all glaciers regardless of topographic location. This suggests that climatic forcings other than solar radiation have become more prominent. Sensitivity analyses indicate that the energy supply of about 5 W m−2, required to produce the observed ice thinning through melting, can be accounted for by a combination of climatic forcings. The direct effect of changing atmospheric composition (“greenhouse effect”) on the net longwave radiation could have contributed less than 1 W m−2. A warming of 0.0 to 0.2°C would translate into an additional downward-directed sensible heat transfer of 0.0 to 1.4 W m−2. A 0.1 to 0.2 g kg−1 increase in specific humidity would, through savings in the latent heat transfer, contribute 2 to 4 W m−2. Long-term station records show little warming trend for East Africa itself. However, mid-tropospheric specific humidity trends of about 0.6 g kg−1 over the past two decades in the equatorial belt have been reported in the literature, and considered to be consequences of “global warming” and the “greenhouse effect”. Viewed in perspective, the ice wastage on Mount Kenya between 1963 and 1987 appears to have been driven primarily by three climatic forcings, conceivably all steered by the “greenhouse effect”: a direct forcing through the net longwave radiation; an indirect forcing through warming and therefore enhanced sensible heat transfer; and another indirect forcing through warming (not necessarily in the region itself), leading to increased (advected) atmospheric moisture, and hence to reduced latent heat transfer, this last line of control being the most important.

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Persistence of Biomarker ATP and ATP-Generating Capability in Bacterial Cells and Spores Contaminating Spacecraft Materials under Earth Conditions and in a Simulated Martian Environment

Applied and Environmental Microbiology ◽

10.1128/aem.00891-08 ◽

2008 ◽

Vol 74 (16) ◽

pp. 5159-5167 ◽

Cited By ~ 16

Author(s):

Patricia Fajardo-Cavazos ◽

Andrew C. Schuerger ◽

Wayne L. Nicholson

Keyword(s):

Bacillus Pumilus ◽

Surface Radiation ◽

Dominant Factor ◽

Bacterial Cells ◽

Gas Composition ◽

Martian Surface ◽

Full Spectrum ◽

Planetary Protection ◽

Surface Conditions ◽

Uv C

ABSTRACTMost planetary protection research has concentrated on characterizing viable bioloads on spacecraft surfaces, developing techniques for bioload reduction prior to launch, and studying the effects of simulated martian environments on microbial survival. Little research has examined the persistence of biogenic signature molecules on spacecraft materials under simulated martian surface conditions. This study examined how endogenous adenosine-5′-triphosphate (ATP) would persist on aluminum coupons under simulated martian conditions of 7.1 mbar, full-spectrum simulated martian radiation calibrated to 4 W m−2of UV-C (200 to 280 nm), −10°C, and a Mars gas mix of CO2(95.54%), N2(2.7%), Ar (1.6%), O2(0.13%), and H2O (0.03%). Cell or spore viabilities ofAcinetobacter radioresistens, Bacillus pumilus, andB. subtiliswere measured in minutes to hours, while high levels of endogenous ATP were recovered after exposures of up to 21 days. The dominant factor responsible for temporal reductions in viability and loss of ATP was the simulated Mars surface radiation; low pressure, low temperature, and the Mars gas composition exhibited only slight effects. The normal burst of endogenous ATP detected during spore germination inB. pumilusandB. subtiliswas reduced by 1 or 2 orders of magnitude following, respectively, 8- or 30-min exposures to simulated martian conditions. The results support the conclusion that endogenous ATP will persist for time periods that are likely to extend beyond the nominal lengths of most surface missions on Mars, and planetary protection protocols prior to launch may require additional rigor to further reduce the presence and abundance of biosignature molecules on spacecraft surfaces.

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Long-term trends in solar radiation and the associated climatic factors over China for 1961-2000

Annales Geophysicae ◽

10.5194/angeo-23-2425-2005 ◽

2005 ◽

Vol 23 (7) ◽

pp. 2425-2432 ◽

Cited By ~ 121

Author(s):

F. Liang ◽

X. A. Xia

Keyword(s):

Solar Radiation ◽

Climatic Factors ◽

Sunshine Duration ◽

Cloud Amount ◽

Atmospheric Composition ◽

Abrupt Decrease ◽

Radiative Processes ◽

Aerosol Loading ◽

Long Term Trends

Abstract. Long-term trends in downwelling solar irradiance and associated climatic factors over China are studied in the paper. Decreasing trends in global and direct radiation are observed over much of China. The largest decrease occurs in South and East China (east of about 100° E and south of about 40° N). The spatial pattern of observed trends in diffuse irradiance is complex and inhomogeneous. An intriguing aspect of trends in global and direct irradiance is the rather abrupt decrease in annual and seasonal mean values from 1978 onward. The decreasing trends in solar radiation in China did not persist into the 1990s. The spatial and temporal patterns of trends in sunshine duration are consistent with that of global and direct irradiance. A decreasing trend in rainy days is observed over much of China, which is in agreement with the secular trend in cloud amount. The fact that trends in cloud amount and solar radiation are quite similar suggests that the cloud amount is not the primary cause for the decrease in solar radiation. Visibility in the eastern part of China has deteriorated heavily as a result of the rapid increase in aerosol loading. The statistical analysis showed that atmospheric transmission under clear conditions decreased rapidly. These facts suggest that the rapid increase in aerosol loading should be one of the principle causes for the decrease in solar radiation. The observed diurnal temperature range decreases remarkably in China, which is closely related to the increase in aerosols. The effects of anthropogenic air pollutants on climate should be further studied and included in the simulation of climate and projection of climate scenario. Keywords. Atmospheric composition and structure (Aerosol and particles; General or miscellaneous) – Meteorology and atmospheric dynamics (Radiative processes)

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The dramatic retreat of Mount Kenya’s glaciers between 1963 and 1987: greenhouse forcing

Annals of Glaciology ◽

10.3189/1992aog16-1-127-133 ◽

1992 ◽

Vol 16 ◽

pp. 127-133 ◽

Cited By ~ 8

Author(s):

Stefan Hastenrath ◽

Phillip D. Kruss

Keyword(s):

Heat Transfer ◽

Solar Radiation ◽

Latent Heat ◽

Greenhouse Effect ◽

Longwave Radiation ◽

Atmospheric Composition ◽

Specific Humidity ◽

Sensitivity Analyses ◽

Sensible Heat ◽

Indirect Forcing

The retreat of the glaciers on Mount Kenya is quantitatively well documented for the intervals 1899–1963 and 1963–1987. The ice recession between 1899 and 1963 was strongly dependent on solar radiation geometry. By contrast, the ice thinning between 1963 and 1987 amounted to about 15 m for all glaciers regardless of topographic location. This suggests that climatic forcings other than solar radiation have become more prominent.Sensitivity analyses indicate that the energy supply of about 5 W m−2, required to produce the observed ice thinning through melting, can be accounted for by a combination of climatic forcings. The direct effect of changing atmospheric composition (“greenhouse effect”) on the net longwave radiation could have contributed less than 1 W m−2. A warming of 0.0 to 0.2°C would translate into an additional downward-directed sensible heat transfer of 0.0 to 1.4 W m−2. A 0.1 to 0.2 g kg−1 increase in specific humidity would, through savings in the latent heat transfer, contribute 2 to 4 W m−2.Long-term station records show little warming trend for East Africa itself. However, mid-tropospheric specific humidity trends of about 0.6 g kg−1 over the past two decades in the equatorial belt have been reported in the literature, and considered to be consequences of “global warming” and the “greenhouse effect”.Viewed in perspective, the ice wastage on Mount Kenya between 1963 and 1987 appears to have been driven primarily by three climatic forcings, conceivably all steered by the “greenhouse effect”: a direct forcing through the net longwave radiation; an indirect forcing through warming and therefore enhanced sensible heat transfer; and another indirect forcing through warming (not necessarily in the region itself), leading to increased (advected) atmospheric moisture, and hence to reduced latent heat transfer, this last line of control being the most important.

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