57 research outputs found
Abundant phosphorus expected for possible life in Enceladus’s ocean
Saturn’s moon Enceladus has a potentially habitable subsurface water ocean that contains canonical building blocks of life (organic and inorganic carbon, ammonia, possibly hydrogen sulfide) and chemical energy (disequilibria for methanogenesis). However, its habitability could be strongly affected by the unknown availability of phosphorus (P). Here, we perform thermodynamic and kinetic modeling that simulates P geochemistry based on recent insights into the geochemistry of the ocean–seafloor system on Enceladus. We find that aqueous P should predominantly exist as orthophosphate (e.g., HPO42−), and total dissolved inorganic P could reach 10−7 to 10−2 mol/kg H2O, generally increasing with lower pH and higher dissolved CO2, but also depending upon dissolved ammonia and silica. Levels are much higher than <10−10 mol/kg H2O from previous estimates and close to or higher than ∼10−6 mol/kg H2O in modern Earth seawater. The high P concentration is primarily ascribed to a high (bi)carbonate concentration, which decreases the concentrations of multivalent cations via carbonate mineral formation, allowing phosphate to accumulate. Kinetic modeling of phosphate mineral dissolution suggests that geologically rapid release of P from seafloor weathering of a chondritic rocky core could supply millimoles of total dissolved P per kilogram of H2O within 105 y, much less than the likely age of Enceladus’s ocean (108 to 109 y). These results provide further evidence of habitable ocean conditions and show that any oceanic life would not be inhibited by low P availability
Measurement of D/H and 13C/12C Ratios in Methane Ice on Eris and Makemake: Evidence for Internal Activity
James Webb Space Telescope's NIRSpec infrared imaging spectrometer observed
the outer solar system dwarf planets Eris and Makemake in reflected sunlight at
wavelengths spanning 1 through 5 microns. Both objects have high albedo
surfaces that are rich in methane ice, with a texture that permits long optical
path lengths through the ice for solar photons. There is evidence for N2 ice
absorption around 4.2 um on Eris, though not on Makemake. No CO ice absorption
is seen at 4.67 um on either body. For the first time, absorption bands of two
heavy isotopologues of methane are observed at 2.615 um (13CH4), 4.33 um
(12CH3D), and 4.57 um (12CH3D). These bands enable us to measure D/H ratios of
(2.5 +/- 0.5) x 10-4 and (2.9 +/- 0.6) x 10-4, along with 13C/12C ratios of
0.012 +/- 0.002 and 0.010 +/- 0.003 in the surface methane ices of Eris and
Makemake, respectively. The measured D/H ratios are much lower than that of
presumably primordial methane in comet 67P/Churyumov-Gerasimenko, but they are
similar to D/H ratios in water in many comets and larger outer solar system
objects. This similarity suggests that the hydrogen atoms in methane on Eris
and Makemake originated from water, indicative of geochemical processes in past
or even ongoing hot environments in their deep interiors. The 13C/12C ratios
are consistent with commonly observed solar system values, suggesting no
substantial enrichment in 13C as could happen if the methane currently on their
surfaces was the residue of a much larger inventory that had mostly been lost
to space. Possible explanations include geologically recent outgassing from the
interiors as well as processes that cycle the surface methane inventory to keep
the uppermost surfaces refreshed
Moderate D/H Ratios in Methane Ice on Eris and Makemake as Evidence of Hydrothermal or Metamorphic Processes in Their Interiors: Geochemical Analysis
Dwarf planets Eris and Makemake have surfaces bearing methane ice of unknown
origin. D/H ratios were recently determined from James Webb Space Telescope
(JWST) observations of Eris and Makemake (Grundy et al., submitted), giving us
new clues to decipher the origin of methane. Here, we develop geochemical
models to test if the origin of methane could be primordial, derived from
CO or CO ("abiotic"), or sourced by organics ("thermogenic"). We find that
primordial methane is inconsistent with the observational data, whereas both
abiotic and thermogenic methane can have D/H ratios that overlap the observed
ranges. This suggests that Eris and Makemake either never acquired a
significant amount of methane during their formation, or their original
inventories were removed and then replaced by a source of internally produced
methane. Because producing abiotic or thermogenic methane likely requires
temperatures in excess of ~150{\deg}C, we infer that Eris and Makemake have
rocky cores that underwent substantial radiogenic heating. Their cores may
still be warm/hot enough to produce methane. This heating could have driven
hydrothermal circulation at the bottom of an ice-covered ocean to generate
abiotic methane, and/or metamorphic reactions involving accreted organic matter
could have occurred in response to heating in the deeper interior, generating
thermogenic methane. Additional analyses of thermal evolution model results and
predictions from modeling of D-H exchange in the solar nebula support our
findings of elevated subsurface temperatures and a lack of primordial methane
on Eris and Makemake. It remains an open question whether their D/H ratios may
have evolved subsequent to methane outgassing. Recommendations are given for
future activities to further test proposed scenarios of abiotic and thermogenic
methane production on Eris and Makemake, and to explore these worlds up close.Comment: Submitted to Icarus, 29 pages, 5 figures, 1 tabl
The Apollo ATCA Platform
We have developed a novel and generic open-source platform - Apollo - which
simplifies the design of custom Advanced Telecommunications Computing
Architecture (ATCA) blades by factoring the design into generic infrastructure
and application-specific parts. The Apollo "Service Module" provides the
required ATCA Intelligent Platform Management Controller, power entry and
conditioning, a powerful system-on-module (SoM) computer, and flexible clock
and communications infrastructure. The Apollo "Command Module" is customized
for each application and typically includes two large field-programmable gate
arrays, several hundred optical fiber interfaces operating at speeds up to 28
Gbps, memories, and other supporting infrastructure. The command and service
module boards can be operated together or independently on the bench without
need for an ATCA shelf.Comment: Submitted to the Proceedings for TWEPP 201
JWST molecular mapping and characterization of Enceladus' water plume feeding its torus
Enceladus is a prime target in the search for life in our solar system,
having an active plume likely connected to a large liquid water subsurface
ocean. Using the sensitive NIRSpec instrument onboard JWST, we searched for
organic compounds and characterized the plume's composition and structure. The
observations directly sample the fluorescence emissions of H2O and reveal an
extraordinarily extensive plume (up to 10,000 km or 40 Enceladus radii) at
cryogenic temperatures (25 K) embedded in a large bath of emission originating
from Enceladus' torus. Intriguingly, the observed outgassing rate (300 kg/s) is
similar to that derived from close-up observations with Cassini 15 years ago,
and the torus density is consistent with previous spatially unresolved
measurements with Herschel 13 years ago, suggesting that the vigor of gas
eruption from Enceladus has been relatively stable over decadal timescales.
This level of activity is sufficient to maintain a derived column density of
4.5x1017 m-2 for the embedding equatorial torus, and establishes Enceladus as
the prime source of water across the Saturnian system. We performed searches
for several non-water gases (CO2, CO, CH4, C2H6, CH3OH), but none were
identified in the spectra. On the surface of the trailing hemisphere, we
observe strong H2O ice features, including its crystalline form, yet we do not
recover CO2, CO nor NH3 ice signatures from these observations. As we prepare
to send new spacecraft into the outer solar system, these observations
demonstrate the unique ability of JWST in providing critical support to the
exploration of distant icy bodies and cryovolcanic plumes.Comment: Accepted for publication in Nature Astronomy on May 17th 202
Comparison between canopy trees and arboreal lower strata of urban semideciduous seasonal forest in Araguari - MG
Planned geological investigations of the Europa Clipper mission
Geological investigations planned for the Europa Clipper mission will examine the formation, evolution, and expression of geomorphic structures found on the surface. Understanding geologic features, their formation, and any recent activity are key inputs in constraining Europa’s potential for habitability. In addition to providing information about the moon’s habitability, the geologic study of Europa is compelling in and of itself. Here we provide a high-level, cross-instrument, and cross-discipline overview of the geologic investigations planned within the Europa Clipper mission. Europa’s fascinating collection of ice-focused geology provides an unparalleled opportunity to investigate the dynamics of icy shells, ice-ocean exchange processes, and global-scale tectonic and tidal stresses. We present an overview of what is currently known about the geology of Europa, from global to local scales, highlighting outstanding issues and open questions, and detailing how the Europa Clipper mission will address them. We describe the mission’s strategy for searching for and characterizing current activity in the form of possible active plumes, thermal anomalies, evidence for surface changes, and extremely fresh surface exposures. The complementary and synergistic nature of the data sets from the various instruments and their integration will be key to significantly advancing our understanding of Europa’s geology
Maximizing the identification of QTL for pre-harvest sprouting resistance using seed dormancy measures in a white-grained hexaploid wheat population
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