Abstract
Discerning the total mass of Mars’ obliquity‐timescale (∼10
5
‐year) exchangeable CO
2
inventory has been elusive for decades due to the unknown adsorptive capacity of its regolith. Now, ...however, the stratigraphy of Mars’ recently discovered South Polar Massive CO
2
Ice Deposit (MCID) provides a record of orbit‐driven CO
2
exchange between its polar cap, atmosphere, and regolith with sufficient constraint to calculate the adsorptive capacity of its regolith and therefore the total mass of its exchangeable CO
2
inventory. We use a numerical climate model and Markov Chain Monte Carlo analysis to show that the observed MCID stratigraphic record is most consistent with a mobile CO
2
inventory of
kg (
mbar, 68% confidence interval) that exchanges on obliquity timescales. We find that adsorptive CO
2
exchange with the regolith on obliquity timescales likely occurs in the depth range of >∼200 m to <∼1 km, with the deeper bound set by thermal processes and adsorptive surface availability. Our best‐fit model yields a peak mean annual surface pressure 40% lower than CO
2
exchange models that neglect an adsorbing regolith. We provide machine‐readable text files of our results to aid future study of Mars’ climate.
Plain Language Summary
Mars’ atmosphere is primarily CO
2
. In addition to atmospheric CO
2
, Mars also has a polar CO
2
ice cap and a reservoir of CO
2
adsorbed in its regolith (i.e., CO
2
molecules forming a thin film on martian soil grains). Determining how much total CO
2
exchanges between the atmosphere, cap, and regolith over orbit‐driven climate cycles is important for understanding Mars’ climatic evolution. We constructed a climate model to calculate how CO
2
exchanges between the atmosphere, cap, and regolith over these ∼10
5
‐year cycles. The model outputs a predicted thickness of alternating layers of CO
2
and H
2
O ice in the CO
2
ice cap. Comparing our model results to the observed layering of the polar cap indicates that ∼100 millibars of CO
2
(∼17 × the current atmospheric mass) can exchange between the atmosphere, polar cap, and regolith during these cycles. Moreover, regolith adsorption likely decreases Mars’ peak atmospheric pressure by ∼40%, which implies that near‐surface habitable environments with liquid water are more difficult to create and sustain on Mars than previously thought.
Key Points
Mars’ mobile CO
2
inventory on obliquity timescales is ∼100 millibar, with adsorptive regolith exchange down to >∼200 m to <∼1 km depth
Mars’ peak surface pressure is ∼40% lower with best‐fit regolith adsorption parameters than when adsorption is ignored
The product of depth and specific surface area is most important regolith property influencing the polar CO
2
ice stratigraphy
Unfolding and Validation of SREM Fluxes Sandberg, I.; Daglis, I. A.; Anastasiadis, A. ...
IEEE transactions on nuclear science,
08/2012, Letnik:
59, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The Standard Radiation Environment Monitor (SREM) belongs to a second generation of instruments in a program established by the European Research and Technology Centre of the European Space Agency ...(ESA) to provide minimum intrusive particle radiation detectors on ESA spacecraft for space weather applications, which are also suitable for scientific investigations.
Covalently cross-linked proteins are among the major modifications caused by the advanced Maillard reaction. So far, the chemical nature of these aggregates is largely unknown. Investigations are ...reported on how the cross-linking unit 2-ammonio-6-{2-(4-ammonio-5-oxido-5-oxopentyl)amino-6,7-dihydroxy-4,5,6,7,8,8a-hexahydroimidazo4,5-
bazepin-4-yl} hexanoate (
7), designated as glucosepan, can be identified and quantified from
d-glucose-bovine serum albumin (BSA) incubations. Independent synthesis and unequivocal structural characterization are given for glucosepan
7. A protocol was established for its determination by LC–MS with electrospray ionization (ESI). BSA and
d-glucose were incubated at 37
°C, pH 7.4 for eight weeks and the time-dependent formation of
7 was observed. Since glucosepan
7 is unstable under acid proteolytic conditions, BSA was cleaved enzymatically. The maximum value obtained from a solution containing 50
g/L BSA and 100
mM
d-glucose after eight weeks incubation time corresponds to an arginine derivatization rate of 1.38±0.07
mmol
7/mol Arg (equivalent to 31.7±1.6
mmol
7/mol BSA). From these results, it seems justified to expect
7 to play an important role in the cross-linking of proteins in vivo as well as in foodstuffs. The structural similarity of glucosepan
7 and pentosidine
1 made it obvious to also look for an eventual parallelism in the respective formation pathways.
The main characteristics of the European Space Agency (ESA) Standard Radiation Environment Monitor (SREM) are outlined. First SREM results from the Project for On-Board Autonomy-I (PROBA-I) and ...INTEGRAL spacecraft are presented.
Understanding the role of parton mass and Casimir color factors in the quantum chromodynamics parton shower represents an important step in characterizing the emission properties of heavy quarks. ...Recent experimental advances in jet substructure techniques have provided the opportunity to isolate and characterize gluon emissions from heavy quarks. In this Letter, the first direct experimental constraint on the charm-quark splitting function is presented, obtained via the measurement of the groomed shared momentum fraction of the first splitting in charm jets, tagged by a reconstructed D^{0} meson. The measurement is made in proton-proton collisions at sqrts=13 TeV, in the low jet transverse-momentum interval of 15≤p_{T}^{jet ch}<30 GeV/c where the emission properties are sensitive to parton mass effects. In addition, the opening angle of the first perturbative emission of the charm quark, as well as the number of perturbative emissions it undergoes, is reported. Comparisons to measurements of an inclusive-jet sample show a steeper splitting function for charm quarks compared with gluons and light quarks. Charm quarks also undergo fewer perturbative emissions in the parton shower, with a reduced probability of large-angle emissions.
A Time Projection Chamber for continuous readout Berger, M.; Berger-Chen, J. C.; Cusanno, F. ...
2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC),
10/2013
Conference Proceeding
A Time Projection Chamber (TPC) with its 3-dimensional tracking and particle identification capabilities is a very powerful detector for high multiplicity events. TPCs are used for tracking in ...several experiments such as ALICE, STAR and many others. A drawback of such devices is the restriction to trigger rates of the order of 1 kHz due to the necessity of a gating grid which prevents ions produced in the amplification region of MWPCs from entering the drift volume. A GEM-TPC has been built which is the GEM-TPC with the largest active volume up to date. The detector has been commissioned with cosmics and particle beams at the FOPI experiment at GSI, and was employed for a physics measurement with a pion beam.
A previously described polymerase chain reaction (PCR) assay (B. Furrer, U. Candrian, C. Hofelein, and J. Luthy, J. Appl. Bacteriol. 70:372-379, 1991) was used to analyze food for the presence of ...Listeria monocytogenes. Food samples were artificially contaminated to develop two procedures to detect the organism following enrichment steps. Procedure A was based on dilution of the enrichment broth followed by lysis of the bacteria and direct analysis of the lysate with PCR. With procedure A and artificially contaminated food samples, it was possible to detect fewer than 10 bacteria per 10 g of food. In procedure B, centrifugation was used to concentrate bacteria before lysis and PCR. With procedure A, 330 naturally contaminated food samples of several types were analyzed. Twenty samples were found to be positive for L. monocytogenes, which was in agreement with the classical culture technique. By using procedure B on a subset of 100 food samples, 14 were found to be positive by PCR whereas the classical culture method detected only 13. Analysis times, including enrichment steps, were 56 and 32 h with procedures A and B, respectively
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