Archives

August 2013


We determine the fraction of G-dwarf stars that could host stable planetary systems based on the observed properties of binaries in the Galactic field, and in various postulated primordial binary populations, which assume that the primordial binary fraction is higher than that in the field.

At optical wavelengths, an exoplanet's signature is essentially reflected light from the host star - several orders of magnitude fainter. Since it is superimposed on the star spectrum its detection has been a difficult observational challenge.

Ranked near the top of the long list of exciting discoveries made with NASA's Kepler photometer is the detection of transiting circumbinary planets. In just over a year the number of such planets went from zero to seven, including a multi-planet system with one of the planets in the habitable zone (Kepler-47).

The Solar System includes two planets --- Mercury and Mars --- significantly less massive than Earth, and all evidence indicates that planets of similar size orbit many stars. In fact, one of the first exoplanets to be discovered is a lunar-mass planet around a millisecond pulsar.

Professor Steven Benner will tell geochemists gathering today (Thursday, 29 August) at the annual Goldschmidt conference that an oxidized mineral form of the element molybdenum, which may have been crucial to the origin of life, could only have been available on the surface of Mars and not on Earth.

Ceres, which orbits the Sun in the asteroid belt between Mars and Jupiter, is a unique body in the Solar System, bearing many similarities to Jupiter's moon Europa and Saturn's moon Enceladus, both considered to be potential sources for harboring life.

Modeling a Near-optimal Genetic Code

Researchers have created a model that may explain the complexities of the origins of life. Their work, which appears in the Journal of the Royal Society Interface, offers new insights into how RNA signaling likely developed into the modern "genetic code."

The characterization of the atmospheres of habitable-zone Earth-mass exoplanets that transit across main-sequence stars, let alone the detection of bio-markers in their atmospheres, will be challenging even with future facilities. It has been noted that white dwarfs (WDs) have long-lived habitable zones and that a large fraction of WDs may host planets.

Water and Low Mass Stars

If water is the source of life, then finding the source of water certainly qualifies as a worthy astrobiological endeavor. Scientists have formulated certain scenarios for how our planet became wet and stayed wet, but other planets may not have been able to tap this same source.

The problem of the contribution of cosmic rays to climate change is a continuing one and one of importance. In principle, at least, the recent results from the CLOUD project at CERN provide information about the role of ionizing particles in 'sensitizing' atmospheric aerosols which might, later, give rise to cloud droplets.

Interstellar ices are layers of molecules deposited on fine dust grains in dark and dense molecular cloud cores. Subsurface ice has been considered in a few astrochemical models, which have shown that it can be of great importance.

For much of human history we have wondered how our solar system formed, and whether there are any other planets like ours around other stars. Only in the last 20 years have we had direct evidence for the existence of exoplanets, with the number of known exoplanets dramatically increasing in recent years, especially with the success of the Kepler mission.

Of the many recently discovered worlds orbiting distant stars, very little is yet known of their chemical composition. With the arrival of new transit spectroscopy and direct imaging facilities, the question of molecular detectability as a function of signal-to-noise (SNR), spectral resolving power and type of planets has become critical.

The discovery of amino acids in meteorites and the detection of glycine in samples returned from a comet to Earth suggest that the interstellar chemistry is capable of producing such complex organic molecules.

A Fluffy Disk Around a Baby Star

The Subaru Telescope's High Contrast Instrument for the Subaru Next Generation Adaptive Optics (HiCIAO) has been used to observe a disk around the young star RY Tau.

Rotation is thought to drive cyclic magnetic activity in the Sun and Sun-like stars. Stellar dynamos, however, are poorly understood owing to the scarcity of observations of rotation and magnetic fields in stars.

Titan, the main satellite of Saturn, has an active cycle of methane in its troposphere. Among other evidence for a mechanism of evaporation at work on the ground, dry lakebeds have been discovered.

Astrobiologists have shown that a key element for life on Earth was likely delivered to our planet on meteorites. Their work indicates that the early Earth was bombarded by meteorites that provided reactive phosphorus. When released in water, this phosphorus could have been incorporated into prebiotic molecules.

A new study has shown how low temperature chemical reactions between iron-containing minerals and water could produce hydrogen 'food' for microorganisms that inhabit pores and cracks in rocks below the ocean floor and parts of the continents.

In the Jupiter-Io system, the moon's motion produces currents along the field lines that connect the moon to the Jupiter's polar regions, where the radio emission is modulated by the currents. Based on this process, we suggest that such modulation of planetary radio emissions may reveal the presence of exomoons around giant planets in exoplanetary systems.

For an astrobiologist, going into the field doesn't have to mean going to another planet. There's plenty to learn about life in the cosmos by studying what our planet has to offer. To help in this exploration, the Lewis and Clark Fund supports the field work of early career scientists.

The NAI team, Virtual Planetary Laboratory (VPL), is interested in how to determine if planets orbiting others stars exhibit signs of life, "biosignatures."

The Astrophysics Division of NASA's Science Mission Directorate is pleased to issue this open call for nominations to serve on the Executive Committee of NASA's Cosmic Origins Program Analysis Group, or COPAG.

Water is an important reservoir species for oxygen in interstellar space and plays a key role in the physics of star formation through cooling by far-infrared emission.

In a new study published in Philosophical Transactions of the Royal Society B, scientists funded by the NASA Astrobiology Institute (NAI) advance a theory about life's origins based on the idea of "reservoir-mediated energy."

Understanding Snowball Earth

During vast ice ages millions of years ago, sheets of glaciers stretched from the poles almost to the equator, covering the Earth in a frozen skin. Conditions on the "snowball Earth," as scientists refer to it, made the planet a completely different place.

Recent high-resolution observations show that protoplanetary disks have various kinds of structural properties or inhomogeneities. These are the consequence of a mixture of a number of physical and chemical processes taking place in the disks.

A Closer Look at HD189733b

Modern, ground-based telescopes and NASA's Kepler spacecraft have now confirmed more than 850 exoplanets, while thousands more await confirmation. The pace of discovery suggests "there are at least 100 billion planets in our galaxy," says John Johnson of Caltech, who works with data from the Kepler mission. "That's mind-boggling."

NASA Astrobiology Strategic Plan Update

The 2014 Astrobiology Strategic Plan is now under construction. It has involved the community in online and face-to-face discussions.

We present Hubble Space Telescope near-infrared transmission spectroscopy of the transiting hot-Jupiter HAT-P-1b.

Planets in M dwarf stars' habitable zones are likely to be tidally locked with orbital periods of order tens of days. This means that the effects of rotation on atmospheric dynamics will be relatively weak, which requires small horizontal temperature gradients above the boundary layer of terrestrial atmospheres.

The purpose of this call for white papers is to solicit community input for alternate science investigations that may be performed using Kepler and are consistent with its probable two-wheel performance.

A lot of people mix up the ozone hole and global warming, believing the hole is a major cause of the world's increasing average temperature. Scientists, on the other hand, have long attributed a small cooling effect to the ozone shortage in the hole.

John Billingham

Keith's note: NASA sources report that John Billingham has passed away. John ran the SETI Program Office when NASA used to do SETI. He also ran life science at NASA Ames.

In a bit of cosmic irony, planets orbiting cooler stars may be more likely to remain ice-free than planets around hotter stars. This is due to the interaction of a star's light with ice and snow on the planet's surface.