Nikita Demidov

Water distribution in Martian permafrost regions from joint analysis of HEND (Mars Odyssey) and MOLA (Mars Global Surveyor) data

We jointly analyze data from the High-Energy Neutron Detector (HEND) onboard the NASA Mars Odyssey spacecraft and data from the Mars Orbiter Laser Altimeter (MOLA) onboard the Mars Global Surveyor spacecraft. The former instrument measures the content of hydrogen (in the form of H2O or OH) in the subsurface layer of soil and the latter instrument measures the surface albedo with respect to the flux of solar energy. We have checked the presence of a correlation between these two data sets in various Martian latitude bands. A significant correlation has been found between these data at latitudes poleward of 40° in the northern hemisphere and at latitudes 40°–60° in the southern hemisphere. This correlation is interpreted as evidence for the presence of stable water ice in these regions under a dry layer of soil whose thickness is determined by the condition for equilibrium between the condensation of water from the atmosphere and its sublimation when heated by solar radiation. For these regions, we have derived an empirical relation between the flux of absorbed solar radiation and the thickness of the top dry layer. It allows the burial depth of the water ice table to be predicted with a sub-kilometer resolution based on near-infrared albedo measurements. We have found no correlation in the southern hemisphere at latitudes >60°, although neutron data also suggest that water ice is present in this region under a layer of dry soil. We conclude that the thickness of the dry layer in this region does not correspond to the equilibrium condition between the water ice table and the atmosphere.

Celerinatantimonas yamalensis sp. nov., a cold-adapted diazotrophic bacterium from a cold permafrost brine

A facultatively anaerobic nitrogen-fixing bacterium, strain C7(T), was isolated from a permafrost cryopeg on the Yamal Peninsula, Russia. Comparative analysis of 16S rRNA gene sequences revealed that this bacterium was closely related to Celerinatantimonas diazotrophica S-G2-2(T) with a similarity of 95.5 %. Strain C7(T) differed from Celerinatantimonas diazotrophica in its ability to hydrolyse gelatin and inability to use d-mannose, melibiose, l-rhamnose, myo-inositol, lactose, lactulose, d-mannitol, trehalose, dl-lactate, glycogen or l-proline as sole carbon sources. In addition, strain C7(T) grew over a temperature range of 0-34 °C with optimum growth at 18-22 °C. The whole-cell fatty acid profile included C16 : 0, C16 : 1ω7, C18 : 1ω7, C17 cyclo and summed feature 2 [comprising C12 : 0 aldehyde and/or unknown fatty acid 10.913 (MIDI designation) and/or iso-C16 : 1/C14 : 0 3-OH]. The DNA G+C content was 44.7 mol%. Strain C7(T) is thus considered to represent a novel species, for which the name Celerinatantimonas yamalensis sp. nov. is proposed. The type strain is C7(T) ( = VKM B-2511(T) = DSM 21888(T)).

Halophilic-psychrotrophic bacteria of an Alaskan cryopeg—a model for astrobiology

Cryopegs, lenses of hypersaline unfrozen soil or water within permafrost, are a model for astrobiology, since free water can only be present on cryogenic bodies and planets in the form of brine. In this paper the diversity of aerobic halophilic-psychrotrophic microorganisms from an Alaskan cryopeg (Barrow Cape) were studied and described for the first time. This cryopeg is characterized by a constant subzero temperature (–7°C), high salinity (total mineralization is about 120 g/L) and isolation from external influences for a geologically significant period of time. Our study has revealed a large number of microorganisms capable of growth at low temperature (4°C) in a wide range of salinities from 5 to 250 g/L of NaCl, the latter being 3 times higher than the natural salt concentration of the Alaskan cryopeg. The microorganisms identified are comprised of four major phyla: Actinobacteria (genera Brevibacterium, Citricoccus, Microbacterium), Firmicutes (genus Paenibacillus), Bacteroidetes (genus Sphingobacterium), and Proteobacteria (genus Ochrobactrum).

Active layer monitoring in Antarctica: an overview of results from 2006 to 2015

Monitoring of active layer thawing depth and active layer thickness (ALT), using mechanical pronging and continuous temperature data logging, has been undertaken under the Circumpolar Active Layer ...