scholarly journals Potential Severe Effects of a Biosphere Collision and Planetary Protection Implications

2019 ◽  
Author(s):  
Robert Walker
Keyword(s):  
Fresh Water ◽  
Liquid Water ◽  
Rna World ◽  
Worst Case ◽  
Protection Measures ◽  
Planetary Protection ◽  
Near Surface ◽  
Heavy Lift ◽  
Interplanetary Flight ◽  
Previous Step

Proposed near surface habitats on Mars include liquid brines, and fresh water below clear ice. A Europa lander could also encounter water. Some are calling for planetary protection measures to be relaxed (Fairén et al, 2017), Others say we have time to study Mars before Earth life is irreversibly introduced (Rummel et al, 2017).. We argue that when our spacecraft may encounter habitable liquid water, we should aim to be even more ambitious. Some commercial components operate at 300 °C. Building on suggestions from a Venus rover study (Sauder et al, 2017), and a Europa cryobot (Wilcox, 2017), we can aim for 100% heat sterilization during interplanetary flight. In the best case, colliding biospheres could be mutually beneficial, or occupy distinct niches, but in the worst case Earth life has no defences (Lederberg, 1999b) and survives only in enclosed habitats. By examining suggestions for RNA world cells (Szostack, 2016) we argue that the worst case for Mars is extinction of all native life. An astrobiological survey is an essential previous step to inform decisions about whether and how to land humans on Mars. The technology for heavy lift for humans to Mars would permit it to be completed rapidly.

Ocean Salinity Aspects of the Ningaloo Niño

2021 ◽  
pp. 1
Author(s):  
Yaru Guo ◽  
Yuanlong Li ◽  
Fan Wang ◽  
Yuntao Wei
Keyword(s):  
Fresh Water ◽  
Large Scale ◽  
Southern Oscillation ◽  
Regional Climate ◽  
Ocean Model ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Surface Salinity ◽  
Near Surface ◽  
Ocean Salinity

AbstractNingaloo Niño – the interannually occurring warming episode in the southeast Indian Ocean (SEIO) – has strong signatures in ocean temperature and circulation and exerts profound impacts on regional climate and marine biosystems. Analysis of observational data and eddy-resolving regional ocean model simulations reveals that the Ningaloo Niño/Niña can also induce pronounced variability in ocean salinity, causing large-scale sea surface salinity (SSS) freshening of 0.15–0.20 psu in the SEIO during its warm phase. Model experiments are performed to understand the underlying processes. This SSS freshening is mutually caused by the increased local precipitation (~68%) and enhanced fresh-water transport of the Indonesian Throughflow (ITF; ~28%) during Ningaloo Niño events. The effects of other processes, such as local winds and evaporation, are secondary (~18%). The ITF enhances the southward fresh-water advection near the eastern boundary, which is critical in causing the strong freshening (> 0.20 psu) near the Western Australian coast. Owing to the strong modulation effect of the ITF, SSS near the coast bears a higher correlation with the El Niño-Southern Oscillation (0.57, 0.77, and 0.70 with Niño-3, Niño-4, and Niño-3.4 indices, respectively) than sea surface temperature (-0.27, -0.42, and -0.35) during 1993-2016. Yet, an idealized model experiment with artificial damping for salinity anomaly indicates that ocean salinity has limited impact on ocean near-surface stratification and thus minimal feedback effect on the warming of Ningaloo Niño.

scholarly journals Morphological evidence for geologically young thaw of ice on Mars: A review of recent studies using high-resolution imaging data

2013 ◽  
Vol 37 (3) ◽  
pp. 289-324 ◽  
Author(s):  
M.R. Balme ◽  
C.J. Gallagher ◽  
E. Hauber
Keyword(s):  
Liquid Water ◽  
Morphological Evidence ◽  
Polar Regions ◽  
Imaging Data ◽  
Patterned Ground ◽  
Large Lakes ◽  
Near Surface ◽  
Crater Lakes ◽  
Recent Climate ◽  
Liquid Flows

Liquid water is generally only meta-stable on Mars today; it quickly freezes, evaporates or boils in the cold, dry, thin atmosphere (surface pressure is about 200 times lower than on Earth). Nevertheless, there is morphological evidence that surface water was extensive in more ancient times, including the Noachian Epoch (∼4.1 Ga to ∼3.7 Ga bp), when large lakes existed and river-like channel networks were incised, and early in the Hesperian Epoch (∼3.7 Ga to ∼2.9 Ga bp), when megafloods carved enormous channels and smaller fluvial networks developed in association with crater-lakes. However, by the Amazonian Epoch (∼3.0 Ga to present), most surface morphogenesis associated with liquid water had ceased, with long periods of water sequestration as ice in the near-surface and polar regions. However, inferences from observations using imaging data with sub-metre pixel sizes indicate that periglacial landscapes, involving morphogenesis associated with ground-ice and/or surface-ice thaw and liquid flows, has been active within the last few million years. In this paper, three such landform assemblages are described: a high-latitude assemblage comprising features interpreted to be sorted clastic stripes, circles and polygons, non-sorted polygonally patterned ground, fluvial gullies, and solifluction lobes; a mid-latitude assemblage comprising gullies, patterned ground, debris-covered glaciers and hillslope stripes; and an equatorial assemblage of linked basins, patterned ground, possible pingos, and channel-and-scarp features interpreted to be retrogressive thaw-slumps. Hypotheses to explain these observations are explored, including recent climate change, and hydrated minerals in the regolith ‘thawing’ to form liquid brines at very low temperatures. The use of terrestrial analogue field sites is also discussed.

A brief overview of photocatalytic mechanisms and pathways in water

2007 ◽  
Vol 55 (12) ◽  
pp. 167-173 ◽  
Author(s):  
P. Pichat
Keyword(s):  
Charge Transfer ◽  
Organic Pollutants ◽  
Liquid Water ◽  
Bound Water ◽  
Near Surface ◽  
Low Concentrations ◽  
Water Layers

This paper outlines the basic events that occur when a semiconductor, in contact with aerated liquid water containing low concentrations of pollutants, is photoexcited. First, the factors favouring this recombination of photoproduced charges are recalled, and the difficulties in decreasing the recombination are underlined. Second, the formation and identification of the species resulting from charge transfer with O2, H2O and pollutants are presented. Third, the reactions involving these species are considered, and methods for assessing their respective importance are critically reviewed. Fourth, on the basis of the view that the photocatalyst surface is covered by tightly bound water layers which hinder the adsorption of many organic pollutants, the hypothesis according to which primary photocatalytic events can take place within the near-surface solution layers is discussed.

scholarly journals Seasonal monitoring of melt and accumulation within the deep percolation zone of the Greenland Ice Sheet and comparison with simulations of regional climate modeling

2018 ◽  
Author(s):  
Achim Heilig ◽  
Olaf Eisen ◽  
Michael MacFerrin ◽  
Marco Tedesco ◽  
Xavier Fettweis
Keyword(s):  
Water Content ◽  
Liquid Water ◽  
Pore Space ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Liquid Water Content ◽  
Water Infiltration ◽  
Near Surface ◽  
Percolation Zone

Abstract. Increasing melt over the Greenland ice sheet (GrIS) recorded over the past years has resulted in significant changes of the percolation regime of the ice sheet. It remains unclear whether Greenland's percolation zone will act as meltwater buffer in the near future through gradually filling all pore space or if near-surface refreezing causes the formation of impermeable layers, which provoke lateral runoff. Homogeneous ice layers within perennial firn, as well as near-surface ice layers of several meter thickness are observable in firn cores. Because firn coring is a destructive method, deriving stratigraphic changes in firn and allocation of summer melt events is challenging. To overcome this deficit and provide continuous data for model evaluations on snow and firn density, temporal changes in liquid water content and depths of water infiltration, we installed an upward-looking radar system (upGPR) 3.4 m below the snow surface in May 2016 close to Camp Raven (66.4779° N/46.2856° W) at 2120 m a.s.l. The radar is capable to monitor quasi-continuously changes in snow and firn stratigraphy, which occur above the antennas. For summer 2016, we observed four major melt events, which routed liquid water into various depths beneath the surface. The last event in mid-August resulted in the deepest percolation down to about 2.3 m beneath the surface. Comparisons with simulations from the regional climate model MAR are in very good agreement in terms of seasonal changes in accumulation and timing of onset of melt. However, neither bulk density of near-surface layers nor the amounts of liquid water and percolation depths predicted by MAR correspond with upGPR data. Radar data and records of a nearby thermistor string, in contrast, matched very well, for both, timing and depth of temperature changes and observed water percolations. All four melt events transferred a cumulative mass of 56 kg/m2 into firn beneath the summer surface of 2015. We find that continuous observations of liquid water content, percolation depths and rates for the seasonal mass fluxes are sufficiently accurate to provide valuable information for validation of model approaches and help to develop a better understanding of liquid water retention and percolation in perennial firn.

scholarly journals The modelled liquid water balance of the Greenland Ice Sheet

2017 ◽  
Author(s):  
Christian R. Steger ◽  
Carleen H. Reijmer ◽  
Michiel R. van den Broeke
Keyword(s):  
Water Balance ◽  
Liquid Water ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Special Focus ◽  
Southeastern Part ◽  
Upward Migration ◽  
Near Surface ◽  
Surface Mass ◽  
Surface Melt

Abstract. Recent studies indicate that the surface mass balance will dominate the Greenland Ice Sheet's (GrIS) contribution to 21st century sea level rise. Consequently, it is crucial to understand the liquid water balance (LWB) of the ice sheet and its response to increasing surface melt. We therefore analyse a firn simulation conducted with SNOWPACK for the GrIS and over the period 1960–2014 with a special focus on the LWB and refreezing. An indirect evaluation of the simulated refreezing climate with GRACE and firn temperature observations indicate a good model performance. Results of the LWB analysis reveal a spatially uniform increase in surface melt during 1990–2014. As a response, refreezing and runoff also indicate positive trends for this period, where refreezing increases with only half the rate of runoff, which implies that the majority of the additional liquid input runs off the ice sheet. However, this pattern is spatially variable as e.g. in the southeastern part of the GrIS, most of the additional liquid input is buffered in the firn layer due to relatively high snowfall rates. The increase in modelled refreezing leads to a general decrease in firn air content and to a substantial increase in near-surface firn temperature in some regions. On the western side of the ice sheet, modelled firn temperature increases are highest in the lower accumulation zone and are primarily caused by the exceptional melt season of 2012. On the eastern side, simulated firn temperature increases more gradually and with an associated upward migration of firn aquifers.

scholarly journals Observed Evolution of the Tropical Atmospheric Water Cycle with Sea Surface Temperature

2020 ◽  
Vol 33 (9) ◽  
pp. 3449-3470
Author(s):  
Erik Höjgård-Olsen ◽  
Hélène Brogniez ◽  
Hélène Chepfer
Keyword(s):  
Liquid Water ◽  
Cloud Cover ◽  
Water Cycle ◽  
Atmospheric Water ◽  
Ice Clouds ◽  
Near Surface ◽  
Surface Precipitation ◽  
Ice Cloud ◽  
Sst Warming ◽  
Water Cloud

AbstractBetter understanding of how moisture, clouds, and precipitation covary under climate warming lacks a comprehensive observational view. This paper analyzes the tropical atmospheric water cycle’s evolution with sea surface temperature (SST), using for the first time, the synergistic dataset of instantaneous observations of the relative humidity profile from the Megha-Tropiques satellite, clouds from the CALIPSO satellite, and near-surface precipitation from the CloudSat satellite, and quantifies their rates of change with SST warming. The dataset is partitioned into three vertical velocity regimes, with cloudy grid boxes categorized by phase (ice or liquid), opacity (opaque or thin), and the presence of near-surface precipitation. Opaque cloud cover is always larger in the presence of near-surface precipitation (high ice clouds especially). Low liquid water clouds in the descending regime dominate for SSTs < 299.25 K, where the free troposphere is dry (~20%), and opaque liquid water cloud cover decreases with SST warming (−8% K−1) and thin liquid water cloud cover stays constant (~20%). High ice clouds dominate the ascending regime in which, for 299.25 < SST < 301.75 K, humidity increases with SST in the lower free troposphere and peaks around 302 K. Over the warm SST range (>301.75 K), in the ascending regime, opaque high ice cloud cover decreases with SST (−13% K−1), while thin ice cloud cover increases (+6% K−1). Over the warm SST range, total cloudiness decreases with warming in all regimes. This paper characterizes fundamental relationships between aspects of the tropical atmospheric water cycle and SST.

Why NASA may be legally required to sterilize Mars samples to protect Earth's biosphere - 19 years minimum until ready to receive unsterilized samples with existing laws - advantages of orbits above GEO for preliminary telerobotic study instead

2020 ◽  
Author(s):  
Robert Walker
Keyword(s):  
Worst Case ◽  
Sample Return ◽  
Planetary Protection ◽  
Blue Green Algae ◽  
Life On Mars ◽  
Previous Sample ◽  
Laplace Plane ◽  
Space Colonization ◽  
To Receive

NASA plans to return a sample from Mars in the 2020s. However they have not yet started on the legal process to return such a sample safely. There are many laws that already exist that protect Earth’s biosphere. Previous sample return studies have shown that we need to build a sample receiving facility to prevent adverse changes to the environment of Earth from a sample return. This paper examines the timescale based on an end to end requirement, that NASA are required to know what it is they need to build before approving funds for the build. This will not be known until the end of the legal process.We find that it is not possible, with current laws and technology, to have a facility ready to receive unsterilized samples on this timescale. However we find that it is possible to sterilize the samples sufficiently for planetary protection requirements while preserving both astrobiological and geological interest. We also propose as an alternative to return the sample to an orbit in the Laplace plane above GEO, as optimal for protection of Earth, the Moon, and other satellites. This will not delay the geological studies as sterilized subsamples can be returned immediately, and it will permit study of unsterilized material in situ telerobotically. We also look at particular worst case scenarios, which have not been considered in detail before, such as the return of a mirror life blue-green algae, capable of living on Mars and almost anywhere on Earth. We suggest that it is a high priority to determine whether Martian life can be safely mixed into the terrestrial biosphere, and to learn what safety protocols are needed to return it safely. We find that there could be life on Mars that can never be mixed into Earth’s biosphere safely. Finding the answers to this should be a top priority for both scientists and space colonization enthusiasts as the future possibilities, and opportunities, that are open to us depend on whether there is life on Mars and what its nature is.

Global Air–Sea Fluxes of Heat, Fresh Water, and Momentum: Energy Budget Closure and Unanswered Questions

2019 ◽  
Vol 11 (1) ◽  
pp. 227-248 ◽  
Author(s):  
Lisan Yu
Keyword(s):  
Surface Energy ◽  
Fresh Water ◽  
Prediction Models ◽  
Weather Prediction ◽  
Ocean Surface ◽  
Surface Radiation ◽  
Global Ocean ◽  
Personal Perspective ◽  
Near Surface ◽  
Water Budgets

The ocean interacts with the atmosphere via interfacial exchanges of momentum, heat (via radiation and convection), and fresh water (via evaporation and precipitation). These fluxes, or exchanges, constitute the ocean-surface energy and water budgets and define the ocean's role in Earth's climate and its variability on both short and long timescales. However, direct flux measurements are available only at limited locations. Air–sea fluxes are commonly estimated from bulk flux parameterization using flux-related near-surface meteorological variables (winds, sea and air temperatures, and humidity) that are available from buoys, ships, satellite remote sensing, numerical weather prediction models, and/or a combination of any of these sources. Uncertainties in parameterization-based flux estimates are large, and when they are integrated over the ocean basins, they cause a large imbalance in the global-ocean budgets. Despite the significant progress that has been made in quantifying surface fluxes in the past 30 years, achieving a global closure of ocean-surface energy and water budgets remains a challenge for flux products constructed from all data sources. This review provides a personal perspective on three questions: First, to what extent can time-series measurements from air–sea buoys be used as benchmarks for accuracy and reliability in the context of the budget closures? Second, what is the dominant source of uncertainties for surface flux products, the flux-related variables or the bulk flux algorithms? And third, given the coupling between the energy and water cycles, precipitation and surface radiation can act as twin budget constraints—are the community-standard precipitation and surface radiation products pairwise compatible?

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