Earth Archives - Page 20 of 34 - Astrobiology

The Rihat Structure

Astrogeology, Caves, Craters, Mountains, Subsurface, Lava Tubes, Desert Worlds, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Mapping, Geodesy, Cartography, Bathymetry, Science Fiction, Status Report

Orbital View Of A Desert World: No, This Is Not Sietch Tabr On Arrakis

by Keith CowingJuly 7, 2024August 23, 2025

This is not Sietch Tabr On Arrakis. It is the Rihat Structure, also known as the Eye of the Sahara – on our home world, Earth.

Surface water regimes for terrestrial planets ranging from 0.1 M⊕ to 10 M⊕. Each limit between regimes is explained in the text. Planets in either the waterworld, Earth-like, or Dune planet regime may be habitable, while desiccated surfaces are uninhabitable. The transition between surface water regimes depends weakly on planetary mass (cf. Cowan & Abbot 2014) -- astro-ph.EP

Analog Studies, Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Origin & Evolution of Life, Status Report, Water/Hycean Worlds & Oceanography

Water Evolution and Inventories of Super-Earths Orbiting Late M-Dwarfs

by Keith CowingJuly 1, 2024July 1, 2024

Super-Earths orbiting M-dwarf stars may be the most common habitable planets in the Universe. However, their habitability is threatened by intense irradiation from their host stars, which drives the escape […]

Cartoon illustrating the physical configuration for sustaining a hydrothermal siphon, with primary driving and resistive forces as applied in this study. Terms are discussed in text and combined in Equation 2. ∆Pv (>0) is primary driving energy in simulations, based on differences in temperature and density between recharging and discharging columns of pore fluid. ∆PR, ∆PD, ∆PC, and ∆PL (≤0) are pressure (energy) losses, depending on formation properties and the extent of secondary convection. ∆Psiph is what remains of ∆Pv after accounting for loss terms, available to drive siphon flow. s = sediment/conductive boundary layer, bu = upper rocky layer, ba = aquifer layer. This cartoon neglects other potential driving forces such as tidal pumping and buoyancy generated by exothermic reactions. -- Journal of Geophysical Research: Planets

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biophysics, Biosignatures & Paleobiology, Enceladus, Europa, Exoplanets, -moons, -comets, Gravitational Biology, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Mapping, Geodesy, Cartography, Bathymetry, Missions & Hardware, ROVs/Submersibles/Diving, Status Report, Water/Hycean Worlds & Oceanography

Sustaining Hydrothermal Circulation With Gravity Relevant to Ocean Worlds

by Keith CowingJune 28, 2024June 28, 2024

Some ocean worlds may sustain active, seafloor hydrothermal systems, but the characteristics and controls on fluid-heat transport in these systems are not well understood.

Ratio of the cumulative collision rate of comets with the Earth analog to the cumulative collision rate of carbonaceous asteroids with the Earth analog. The cumulative collision rates are reset at the time of the Moon-forming impact; and the ratio is set to 0 when the cumulative collision rates of carbonaceous asteroids (denominator) equals 0. So the dashed line shows the number of collisions with comets relative to the number of collisions with carbonaceous asteroids (weighted by their respective numbers in our simulations) on Earth since gas disk dispersal until the Moon-forming impact; and the solid line shows the same relative number since the Moon-forming impact until the end of the simulation. While cumulative collision rates of comets with Earth are ≃ 4 orders of magnitude smaller than those of carbonaceous asteroids before the Moon-forming impact, they are between 3 and 7 orders of magnitude smaller after the Moon-forming impact. In 30% of our simulations, there is about 1 comet every 103 carbonaceous asteroids colliding with the Earth after the Moon-forming event, which is consistent with the total cometary mass expected during late accretion. -- astro-ph.EP

Astrochemistry, Astrogeology, Biogeochemical Cycles & Geobiology, Comets and Asteroids, Extinction events, Gaia - Planetary Perspectives, Habitable Zones, Impact events, Meteorites & Asteroids, Moon, Origin & Evolution of Life, Status Report, Water/Hycean Worlds & Oceanography

Crash Chronicles: Relative Contribution From Comets and Carbonaceous Asteroids to Earth’s Volatile Budget In The Context of an Early Instability

by Keith CowingJune 25, 2024June 25, 2024

Recent models of solar system formation suggest that a dynamical instability among the giant planets happened within the first 100 Myr after disk dispersal, perhaps before the Moon-forming impact. As […]

Optical image of the clastic matrix region in LAR 12252 that was studied using S-XANES. Notable phases include enstatite (example outlined in red), sulphides (example outlined in yellow), a small chondrule fragment (outlined in orange), and fine matrix (example highlighted in pink). b Corresponding map calculated from the SXANES spectra of the region shown in a, showing the amplitude of the H-S peak at each point normalised to the average amplitude of point spectra measured from chondrule mesostasis. Black pixels correspond to points where the S-XANES spectra that did not contain a resolvable H-S peak. White pixels correspond to points where the SXANES spectra could not be fitted due to their quality or noise in the spectra. -- astro-ph.EP

Astrochemistry, Astrogeology, Biogeochemical Cycles & Geobiology, Comets and Asteroids, Meteorites & Asteroids, Status Report, Water/Hycean Worlds & Oceanography

The Source of Hydrogen in Earth’s Building Blocks

by Keith CowingJune 21, 2024June 21, 2024

Despite being pivotal to the habitability of our planet, the process by which Earth gained its present-day hydrogen budget is unclear. Due to their isotopic similarity to terrestrial rocks across […]

a–c The N abundance and (d–f) δ15N in the bulk silicate reservoir as a function of the residual N fraction after evaporation. (a, d) Under relatively reducing conditions; (b, e) Relatively oxidizing conditions. (c, f) The modeled N concentration and δ15N in the bulk silicate part at the oxygen fugacity (log fO2) of Earth’s accreting materials (~IW-3 to IW-1). Earth’s core/mantle mass ratio was also used for models in (a) and (b). The fO2 affects the N partition coefficient between metal and silicate (Dmetal/silicateN) and the N species in silicate melts21,22,24,31,33, which consequently controls the equilibrium N isotope fractionation between vapor (N2) and silicate melt (103lnαN2-silicate) (Fig. 1c). The green areas represent the values of the bulk silicate Earth. The red and blue lines in upper panels represent the initial N concentrations (Cinit) of 500 and 1000 ppm in planetesimals before evaporation, respectively. The dash lines refer to the modeling results at different Dmetal/silicateN values. The yellow, blue, and red shadow regions in the lower panels represent the modeled δ15N in the bulk silicate reservoir with an initial δ15N (δ15Ninit) of +20‰, 0‰, and −20‰, respectively. -- Nature Communications

Astrochemistry, Astrogeology, Biogeochemical Cycles & Geobiology, Status Report

Shaping Earth’s Initial Nitrogen Budget

by Keith CowingJune 18, 2024June 18, 2024

The relative roles of protoplanetary differentiation versus late accretion in establishing Earth’s life-essential volatile element inventory are being hotly debated.

The heliosphere at the end of the simulation at 44 years in the meridional plane at y = 0 au (for the model coordinate system, see ‘Description of the numerical model’ in Methods). Contours are speed. The heliosphere shrinks to 0.22 au at the nose. It maintains a long cometary shape and exposes all the planets to the cold dense ISM material.-- Nature Astronomy

Arctic / Antarctic / Alpine, Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Fossils & Paleontology, Habitable Zones, Icy Worlds, Interstellar, Press Release

Our Solar System May Have Passed Through Dense Interstellar Clouds 2 Million Years Ago, Altering Earth’s Climate

by Keith CowingJune 11, 2024June 11, 2024

Around two million years ago, Earth was a very different place, with our early human ancestors living alongside saber-toothed tigers, mastodons, and enormous rodents. And, depending on where they were, […]

Noctilucent clouds seen in the German city of Kühlungsborn. Its delicate and complex structure and flow indicate the presence of atmospheric gravity waves and turbulence. CREDIT Gerd Baumgarten/Leibniz-Institute of Atmospheric Physics

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biophysics, Press Release, Space Weather & Heliophysics

Earth And Space Share The Same Turbulence

by Keith CowingJune 7, 2024June 7, 2024

In a paper published in Geophysical Research Letters, researchers have discovered that the turbulence in the thermosphere exhibits the same physical laws as the wind in the lower atmosphere. Furthermore, […]

Water-rich Exoplanet Atmosphere -- NASA

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Habitable Zones, Origin & Evolution of Life, Press Release, Water/Hycean Worlds & Oceanography

Fresh Findings: Earliest Evidence Of Life-bringing Freshwater On Earth

by Keith CowingJune 5, 2024June 5, 2024

New Curtin-led research has found evidence that fresh water on Earth, which is essential for life, appeared about four billion years ago – five hundred million years earlier than previously […]

Thin-section micrograph illustrating micritic crust at surface of stromatolite -- GSA

Biosignatures & Paleobiology, Fossils & Paleontology, Microbiology & Virology, Press Release

New Vestiges Of The First Life On Earth Discovered In Saudi Arabia

by Keith CowingJune 3, 2024June 3, 2024

Stromatolites are the earliest geological record of life on Earth. These curious biotic structures are made of algae carpets growing toward the light and precipitating carbonates.