Archives

December 2019


Context. While radiative cooling of interstellar grains is a well-known process, little detail is known about the cooling of grains with an icy mantle that contains volatile adsorbed molecules.

Robustly modeling the inner edge of the habitable zone is essential for determining the most promising potentially habitable exoplanets for atmospheric characterization.

Keith's note: I was on Deutsche Welle TV today talking about the Mars 2020 rover mission and its implications for Astrobiology.

Dust plays a crucial role in the life and health of our planet. In our modern world, dust-borne nutrients traveling in great dust storms from the Saharan Desert fertilize the soil in the Amazon Rainforest and feed photosynthetic organisms like algae in the Atlantic Ocean. In turn, it is those organisms that breathe in carbon dioxide and expel oxygen.

The James Webb Space Telescope (JWST) is expected to revolutionize our understanding of Jovian worlds over the coming decade. However, as we push towards characterizing cooler, smaller, "terrestrial-like" planets, dedicated next-generation facilities will be required to tease out the small spectral signatures indicative of biological activity.

The most widely-studied mechanism of mass loss from extrasolar planets is photoevaporation via XUV ionization, primarily in the context of highly irradiated planets.

The search for water-rich Earth-sized exoplanets around low-mass stars is rapidly gaining attention because they represent the best opportunity to characterize habitable planets in the near future.

Aims. Due to the limitations of current computational technology, the fragmentation and isomerization products of vibrationally-excited polycyclic aromatic hydrocarbon (PAH) molecules and their derivatives are poorly studied.

We are on the verge of characterizing the atmospheres of terrestrial exoplanets in the habitable zones of M dwarf stars.

Exoplanet discoveries have motivated numerous efforts to find unseen populations of exomoons, yet they have been unsuccessful. A plausible explanation is that most discovered planets are located on close-in orbits, which would make their moons prone to tidal evolution and orbital detachment.

The primary goal is to train the next generation of scientists and engineers, enabling NASA to meet future research and development challenges in space life sciences.

Every school child learns about the water cycle--evaporation, condensation, precipitation, and collection. But what if there were a deep Earth component of this process happening on geologic timescales that makes our planet ideal for sustaining life as we know it?

When exposed to the high energy X-ray and ultraviolet radiation of a very active star, water vapor in the upper atmospheres of planets can be photodissociated and rapidly lost to space.

Researchers have discovered gigantic clouds of gaseous carbon spanning more than a radius of 30,000 light-years around young galaxies using the Atacama Large Millimeter/submillimeter Array (ALMA).

Researchers have created the first map of wind circulation in the upper atmosphere of a planet besides Earth, using data from NASA's MAVEN spacecraft that were collected during the last two years.

2I/Borisov is the second interstellar object (ISO) after 'Oumuamua (Meech et al. 2017), but differs from 'Oumuamua drastically with its extensive cometary activity. A key ingredient to understand the nature of this comet is its size.

The discovery of terrestrial exoplanets, planets that orbit stars outside the solar system, has been one of the most significant developments in modern astronomy.

2I/Borisov is the first-ever observed interstellar comet (and the second detected interstellar object). It was discovered on 30 August 2019 and has a heliocentric orbital eccentricity of ~ 3.35, corresponding to a hyperbolic orbit that is unbound to the Sun.

Recently, transmission spectroscopy in the atmospheres of the TRAPPIST-1 planets revealed flat and featureless absorption spectra, which rule out cloud-free hydrogen-dominated atmospheres. Earth-sized planets orbiting TRAPPIST-1 likely have either a clear or a cloudy/hazy hydrogen-poor atmosphere.

With the spacewalk season on hold until next year, ESA astronaut Luca Parmitano took his time to prepare the orbital home for new, tiny and incredibly resistant passengers. Rotifers, commonly called wheel animals, are usually less than a millimetre in size and usually found in fresh water and moist soil.

A new paper published in Geophysical Research Letters will help by providing a map of water ice believed to be as little as an inch (2.5 centimeters) below the surface.

A scene that first played out on the Moon in 1972 happened again, years later, in Hawaii. While exploring the lunar surface, Apollo 17 astronaut and geologist Harrison Schmitt spotted some bright orange soil - an important clue about the Moon's volcanic history. You can hear the excitement in his voice in recordings, but mission control in Houston couldn't see what was so remarkable in the video beamed back to Earth.

Before about 500 million years ago, most probably our planet experienced temporary snowball conditions, with continental and sea ices covering a large fraction of its surface.

Atmospheric compositions can provide powerful diagnostics of formation and migration histories of planetary systems.

Interstellar Objects (ISO) passing through our Solar System offer a rare opportunity to probe the physical and chemical processes involved in solid body and planet formation in extrasolar systems.

The most extensive survey of atmospheric chemical compositions of exoplanets to date has revealed trends that challenge current theories of planet formation and has implications for the search for water in the solar system and beyond.

New research strongly suggests that the distinct 'oxygenation events' that created Earth's breathable atmosphere happened spontaneously, rather than being a consequence of biological or tectonic revolutions.

Aquatic photosynthesis plays a major role in carbon fixation and O2 production on Earth. In this paper, we analyze the prospects for oxygenic photosynthesis in aquatic environments on Earth-analogs around F-, G-, K- and M-type stars.

We review the state of knowledge on the origin of Earth's water. Empirical constraints come from chemical and isotopic measurements of solar system bodies and of Earth itself. Dynamical models have revealed pathways for water delivery to Earth during its formation; most are anchored to specific models for terrestrial planet formation.

Saturn's icy moon Enceladus is of great interest to scientists due to its subsurface ocean, making it a prime target for those searching for life elsewhere.

The presence of a liquid solvent is widely regarded as an essential prerequisite for habitability. We investigate the conditions under which worlds outside the habitable zones of stars are capable of supporting liquid solvents on their surface over geologically significant timescales via combined radiogenic and primordial heat.

Polycyclic aromatic hydrocarbons (PAHs) are key species in astrophysical environments in which vacuum ultraviolet (VUV) photons are present, such as star-forming regions.

High-resolution scans of a 4.6-billion-year-old meteorite have revealed 'fossilised' ice. It is the first direct evidence of early asteroids incorporating frozen water into their matrix when they formed.

Two million-year old ice from Antarctica recently uncovered by a team of researchers provides a clearer picture into the connections between greenhouse gases and climate in ancient times and will help scientists understand future climate change.

An international team of astronomers have made a historic discovery using the William Herschel Telescope (WHT), detecting gas molecules in a comet which has tumbled into our solar system from another star. It is the first time that astronomers have been able to detect this type of material in an interstellar object.

The eyes of the extinct sea scorpion Jaekelopterus rhenaniae have the same structure as the eyes of modern horseshoe crabs (Limulidae). The compound eyes of the giant predator exhibited lens cylinders and concentrically organized sensory cells enclosing the end of a highly specialized cell.

Last night our weather shifted from sunny skies to low-cloud, light snow and light but gusty winds, our highest gust today being about 30 knots. The forecast is for more of the same so we must be prepared tonight for high winds that could descend upon us at most any time.

The Network for Life Detection (NfoLD) is a NASA Research Coordination Network focused on advancing life detection research by building a strong, diverse, and interactive community of scientists and technologists.

The atmosphere of exoplanets has been studied extensively in recent years, using numerical models to retrieve chemical composition, dynamical circulation or temperature from data.

Small exoplanets of nearby M dwarf stars present the possibility to find and characterize habitable worlds within the next decade. TRAPPIST-1, an ultracool M dwarf star, was recently found to have seven Earth-sized planets of predominantly rocky composition.

Habitable planets are often defined as terrestrial worlds capable of maintaining surface liquid water. As a result, atmospheric water vapor can be a critical indicator of habitability. Thus, habitability-themed exoplanet investigations emphasize detection of water vapor signatures for their targets.

In the 20th century the scientific search for extraterrestrial intelligence began, and the Drake equation was proposed to estimate the number of extraterrestrial species humanity could attempt to detect, N.

A Cornell University senior has come up with a way to discern life on exoplanets loitering in other cosmic neighborhoods: a spectral field guide.

Chemical evolution is essential in understanding the origins of life. We present a theory for the evolution of molecule masses and show that small molecules grow by random diffusion and large molecules by a preferential attachment process leading eventually to life's molecules.

Scientists studying the weather and climate of Titan, Saturn's largest moon, have reported a significant seasonal variation in its energy budget - that is the amount of solar energy absorbed by the celestial body and the thermal energy it emits.

Chemolithotrophic microorganisms derive their energy from inorganic sources. Research into the physiological processes of these organisms - which are grown on meteorite - provides new insights into the potential of extraterrestrial materials as a source of accessible nutrients and energy for microorganisms of the early Earth.

Cometary comae are generally depleted in nitrogen. The main carriers for volatile nitrogen in comets are NH3 and HCN. It is known that ammonia readily combines with many acids like e.g. HCN, HNCO, HCOOH, etc. encountered in the interstellar medium as well as in cometary ice to form ammonium salts (NH4+X-) at low temperatures.

A new tool that simultaneously compares 1.4 million genetic sequences can classify how species are related to each other at far larger scales than previously possible. Described today in Nature Biotechnology by researchers from the Centre for Genomic Regulation in Barcelona, the technology can reconstruct how life has evolved over hundreds of millions of years and makes important inroads for the ambition to understand the code of life for every living species on Earth.

Earth's breathable atmosphere is key for life, and a new study suggests that the first burst of oxygen was added by a spate of volcanic eruptions brought about by tectonics.

The famous Miller-Urey experiment, which provides essential information on the prebiotic synthesis of the molecules of life, still has many obscure points.

When NASA's James Webb Space Telescope launches in 2021, one of its most anticipated contributions to astronomy will be the study of exoplanets -- planets orbiting distant stars.

We present new observations of the transmission spectrum of the hot Jupiter WASP-6b both from the ground with the Very Large Telescope (VLT) FOcal Reducer and Spectrograph (FORS2) from 0.45-0.83 μm, and space with the Transiting Exoplanet Survey Satellite (TESS) from 0.6-1.0 μm and the Hubble Space Telescope (HST) Wide Field Camera 3 from 1.12-1.65 μm.

We explore the application of machine learning based on mixture density neural networks (MDNs) to the interior characterization of low-mass exoplanets up to 25 Earth masses constrained by mass, radius, and fluid Love number k2.

The Atmospheric Radiation Interaction Simulator (AtRIS) was used to model the altitude-dependent Venusian absorbed dose and the Venusian dose equivalent.