Detection of ferrihydrite in Martian red dust records ancient cold and wet co...S辿rgio Sacani
油
Iron oxide-hydroxide minerals in Martian dust provide crucial insights into
Mars past climate and habitability. Previous studies attributed Mars red color
to anhydrous hematite formed through recent weathering. Here, we show that
poorly crystalline ferrihydrite (Fe5O8H 揃 nH2O) is the dominant iron oxidebearing phase in Martian dust, based on combined analyses of orbital, in-situ,
and laboratory visible near-infrared spectra. Spectroscopic analyses indicate
that a hyperfine mixture of ferrihydrite, basalt and sulfate best matches Martian dust observations. Through laboratory experiments and kinetic calculations, we demonstrate that ferrihydrite remains stable under present-day
Martian conditions, preserving its poorly crystalline structure. The persistence
of ferrihydrite suggests it formed during a cold, wet period on early Mars
under oxidative conditions, followed by a transition to the current hyper-arid
environment. This finding challenges previous models of continuous dry oxidation and indicates that ancient Mars experienced aqueous alteration before
transitioning to its current desert state.
Wepresent the localizationandhostgalaxyofFRB20190208A, arepeatingsourceof fast radiobursts (FRBs) discoveredusingCHIME/FRB.Aspartof thePinpointingREpeatingChImeSourceswithEVNdishesrepeater localizationprogramon theEuropeanVLBINetwork (EVN),wemonitoredFRB20190208Afor 65.6hr at 1.4GHzanddetectedasingleburst,whichledtoitsverylongbaselineinterferometrylocalizationwith260mas uncertainty(2).Follow-upopticalobservationswiththeMMTObservatory(i25.7mag(AB))foundnovisible hostattheFRBposition.SubsequentdeeperobservationswiththeGranTelescopioCanarias,however,revealedan extremelyfaintgalaxy(r=27.32賊0.16mag),verylikely(99.95%)associatedwithFRB20190208A.Giventhe dispersionmeasureoftheFRB(580pccm3),eventhemostconservativeredshiftestimate( ~ z 0.83 max )implies TheAstrophysicalJournalLetters,977:L4(17pp),2024December10 https://doi.org/10.3847/2041-8213/ad8ce1 息2024.TheAuthor(s).PublishedbytheAmericanAstronomicalSociety. 30BantingFellow. 31McGillSpaceInstituteFellow. 32 FRQNTPostdoctoralFellow. Originalcontent fromthisworkmaybeusedunder theterms of theCreativeCommonsAttribution4.0licence.Anyfurther distributionofthisworkmustmaintainattributiontotheauthor(s)andthetitle of thework, journalcitationandDOI. 1The Astrophysical Journal Letters, 977:L4 (17pp), 2024 December 10 Hewitt et al. that this is the lowest-luminosity FRB host to date (108 Le), even less luminous than the dwarf host of FRB20121102A. We investigate how localization precision and the depth of optical imaging affect host association and discuss the implications of such a low-luminosity dwarf galaxy. Unlike the other repeaters with low-luminosity hosts, FRB 20190208A has a modest Faraday rotation measure of a few tens of rad m2, and EVN plus Very Large Array observations reveal no associated compact persistent radio source. We also monitored FRB20190208A for 40.4hr over 2yr as part of the Extragalactic Coherent Light from Astrophysical Transients repeating FRB monitoring campaign on the Nan巽ay Radio Telescope and detected one burst. Our results demonstrate that, in some cases, the robust association of an FRB with a host galaxy will require both high localization precision and deep optical follow-up. Unified Astronomy Thesaurus concepts: Radio bursts (1339); Radio transient sources (2008); Very long baseline interferometry (1769); Dwarf galaxies (416)
Detection of ferrihydrite in Martian red dust records ancient cold and wet co...S辿rgio Sacani
油
Iron oxide-hydroxide minerals in Martian dust provide crucial insights into
Mars past climate and habitability. Previous studies attributed Mars red color
to anhydrous hematite formed through recent weathering. Here, we show that
poorly crystalline ferrihydrite (Fe5O8H 揃 nH2O) is the dominant iron oxidebearing phase in Martian dust, based on combined analyses of orbital, in-situ,
and laboratory visible near-infrared spectra. Spectroscopic analyses indicate
that a hyperfine mixture of ferrihydrite, basalt and sulfate best matches Martian dust observations. Through laboratory experiments and kinetic calculations, we demonstrate that ferrihydrite remains stable under present-day
Martian conditions, preserving its poorly crystalline structure. The persistence
of ferrihydrite suggests it formed during a cold, wet period on early Mars
under oxidative conditions, followed by a transition to the current hyper-arid
environment. This finding challenges previous models of continuous dry oxidation and indicates that ancient Mars experienced aqueous alteration before
transitioning to its current desert state.
Wepresent the localizationandhostgalaxyofFRB20190208A, arepeatingsourceof fast radiobursts (FRBs) discoveredusingCHIME/FRB.Aspartof thePinpointingREpeatingChImeSourceswithEVNdishesrepeater localizationprogramon theEuropeanVLBINetwork (EVN),wemonitoredFRB20190208Afor 65.6hr at 1.4GHzanddetectedasingleburst,whichledtoitsverylongbaselineinterferometrylocalizationwith260mas uncertainty(2).Follow-upopticalobservationswiththeMMTObservatory(i25.7mag(AB))foundnovisible hostattheFRBposition.SubsequentdeeperobservationswiththeGranTelescopioCanarias,however,revealedan extremelyfaintgalaxy(r=27.32賊0.16mag),verylikely(99.95%)associatedwithFRB20190208A.Giventhe dispersionmeasureoftheFRB(580pccm3),eventhemostconservativeredshiftestimate( ~ z 0.83 max )implies TheAstrophysicalJournalLetters,977:L4(17pp),2024December10 https://doi.org/10.3847/2041-8213/ad8ce1 息2024.TheAuthor(s).PublishedbytheAmericanAstronomicalSociety. 30BantingFellow. 31McGillSpaceInstituteFellow. 32 FRQNTPostdoctoralFellow. Originalcontent fromthisworkmaybeusedunder theterms of theCreativeCommonsAttribution4.0licence.Anyfurther distributionofthisworkmustmaintainattributiontotheauthor(s)andthetitle of thework, journalcitationandDOI. 1The Astrophysical Journal Letters, 977:L4 (17pp), 2024 December 10 Hewitt et al. that this is the lowest-luminosity FRB host to date (108 Le), even less luminous than the dwarf host of FRB20121102A. We investigate how localization precision and the depth of optical imaging affect host association and discuss the implications of such a low-luminosity dwarf galaxy. Unlike the other repeaters with low-luminosity hosts, FRB 20190208A has a modest Faraday rotation measure of a few tens of rad m2, and EVN plus Very Large Array observations reveal no associated compact persistent radio source. We also monitored FRB20190208A for 40.4hr over 2yr as part of the Extragalactic Coherent Light from Astrophysical Transients repeating FRB monitoring campaign on the Nan巽ay Radio Telescope and detected one burst. Our results demonstrate that, in some cases, the robust association of an FRB with a host galaxy will require both high localization precision and deep optical follow-up. Unified Astronomy Thesaurus concepts: Radio bursts (1339); Radio transient sources (2008); Very long baseline interferometry (1769); Dwarf galaxies (416)
Coordination and Response: The Nervous System | IGCSE BiologyBlessing Ndazie
油
This comprehensive IGCSE Biology presentation explains the nervous system, focusing on how the body coordinates and responds to stimuli. Learn about the central and peripheral nervous systems, reflex actions, neurons, synapses, and the role of neurotransmitters. Understand the differences between voluntary and involuntary responses and how the nervous system interacts with other body systems. Ideal for Cambridge IGCSE students preparing for exams!
Variation and Natural Selection | IGCSE BiologyBlessing Ndazie
油
This extensive slide deck provides a detailed exploration of variation and natural selection for IGCSE Biology. It covers key concepts such as genetic and environmental variation, types of variation (continuous and discontinuous), mutation, evolution, and the principles of natural selection. The presentation also explains Darwins theory of evolution, adaptation, survival of the fittest, selective breeding, antibiotic resistance in bacteria, and speciation. With illustrative diagrams, real-life examples, and exam-style questions, this resource is ideal for IGCSE students, teachers, and independent learners preparing for exams.
Biowaste Management and Its Utilization in Crop Production.pptxVivek Bhagat
油
Bio-waste management involves the collection, treatment, and recycling of organic waste to reduce environmental impact. Proper utilization in crop production includes composting, vermiculture, and biofertilizers, enhancing soil fertility and sustainability. This eco-friendly approach minimizes waste, improves crop yield, and promotes sustainable agriculture.
Hormones and the Endocrine System | IGCSE BiologyBlessing Ndazie
油
This IGCSE Biology presentation explores hormones and the endocrine system, explaining their role in controlling body functions. Learn about the differences between nervous and hormonal control, major endocrine glands, key hormones (such as insulin, adrenaline, and testosterone), and homeostasis. Understand how hormones regulate growth, metabolism, reproduction, and the fight-or-flight response. A perfect resource for Cambridge IGCSE students preparing for exams!
The Solar Systems passage through the Radcliffe wave during the middle MioceneS辿rgio Sacani
油
As the Solar System orbits the Milky Way, it encounters various Galactic environments, including dense regions of the
interstellar medium (ISM). These encounters can compress the heliosphere, exposing parts of the Solar System to the ISM, while also
increasing the influx of interstellar dust into the Solar System and Earths atmosphere. The discovery of new Galactic structures, such
as the Radcliffe wave, raises the question of whether the Sun has encountered any of them.
Aims. The present study investigates the potential passage of the Solar System through the Radcliffe wave gas structure over the past
30 million years (Myr).
Methods. We used a sample of 56 high-quality, young (30 Myr) open clusters associated with a region of interest of the Radcliffe
wave to trace its motion back and investigate a potential crossing with the Solar Systems past orbit.
Results. We find that the Solar Systems trajectory intersected the Radcliffe wave in the Orion region. We have constrained the timing
of this event to between 18.2 and 11.5 Myr ago, with the closest approach occurring between 14.8 and 12.4 Myr ago. Notably, this
period coincides with the Middle Miocene climate transition on Earth, providing an interdisciplinary link with paleoclimatology. The
potential impact of the crossing of the Radcliffe wave on the climate on Earth is estimated. This crossing could also lead to anomalies
in radionuclide abundances, which is an important research topic in the field of geology and nuclear astrophysics.
際際滷 describe the role of ABA in plant abiotic stress mitigation. 際際滷 include role of ABA in cold stress, drought stress and salt stress mitigation along with role of ABA in stomatal regulation.
Effects of various chemical factors on in-vitro growth of tissue culture. Various factors like Environmental, Chemical, Physical, and photoperiod affect plant tissue in vitro growth. 際際滷 discuss about the chemical factors like Macronutrients, micronutrients, PGR as well include the new chemical factor that are descovered recently like Meta-topolin, TDZ etc.
