Search for Life on Distant Worlds

NASA is bringing together experts spanning a variety of scientific fields for an unprecedented initiative dedicated to the search for life on planets outside our Solar System.

The Nexus for Exoplanet System Science, or “NExSS”, hopes to better understand the various components of an exoplanet, as well as how the planet stars and neighbor planets interact to support life.

“This interdisciplinary endeavor connects top research teams and provides a synthesized approach in the search for planets with the greatest potential for signs of life,” says Jim Green, NASA’s Director of Planetary Science. “The hunt for exoplanets is not only a priority for astronomers, it’s of keen interest to planetary and climate scientists as well.”

The study of exoplanets – planets around other stars – is a relatively new field. The discovery of the first exoplanet around a star like our sun was made in 1995. Since the launch of NASA’s Kepler space telescope six years ago, more than 1,000 exoplanets have been found, with thousands of additional candidates waiting to be confirmed. Scientists are developing ways to confirm the habitability of these worlds and search for biosignatures, or signs of life.

The key to this effort is understanding how biology interacts with the atmosphere, geology, oceans, and interior of a planet, and how these interactions are affected by the host star. This “system science” approach will help scientists better understand how to look for life on exoplanets.

NExSS will tap into the collective expertise from each of the science communities supported by NASA’s Science Mission Directorate:

• Earth scientists develop a systems science approach by studying our home planet.
• Planetary scientists apply systems science to a wide variety of worlds within our Solar System.
• Heliophysicists add another layer to this systems science approach, looking in detail at how the Sun interacts with orbiting planets.
• Astrophysicists provide data on the exoplanets and host stars for the application of this systems science framework.

NExSS will bring together these prominent research communities in an unprecedented collaboration, to share their perspectives, research results, and approaches in the pursuit of one of humanity’s deepest questions: Are we alone?

The team will help classify the diversity of worlds being discovered, understand the potential habitability of these worlds, and develop tools and technologies needed in the search for life beyond Earth.

Dr. Paul Hertz, Director of the Astrophysics Division at NASA notes, “NExSS scientists will not only apply a systems science approach to existing exoplanet data, their work will provide a foundation for interpreting observations of exoplanets from future exoplanet missions such as TESS, JWST, and WFIRST.” The Transiting Exoplanet Survey Satellite (TESS) is working toward a 2017 launch, with the James Webb Space Telescope (JWST) scheduled for launch in 2018. The Wide-field Infrared Survey Telescope is currently being studied by NASA for a launch in the 2020’s.

NExSS will be led by Natalie Batalha of NASA’s Ames Research Center, Dawn Gelino with NExScI, the NASA Exoplanet Science Institute, and Anthony del Genio of NASA’s Goddard Institute for Space Studies. The NExSS project will also include team members from 10 different universities and two research institutes. These teams were selected from proposals submitted across NASA’s Science Mission Directorate.

The Berkeley/Stanford University team is led by James Graham. This "Exoplanets Unveiled" group will focus on this question: “What are the properties of exoplanetary systems, particularly as they relate to their formation, evolution, and potential to harbor life?”

Daniel Apai leads the “Earths in Other Solar Systems” team from the University of Arizona. The EOS team will combine astronomical observations of exoplanets and forming planetary systems with powerful computer simulations and cutting-edge microscopic studies of meteorites from the early Solar System to understand how Earth-like planets form and how biocritical ingredients — C, H, N, O-containing molecules — are delivered to these worlds.

The Arizona State University team will take a similar approach. Led by Steven Desch, this research group will place planetary habitability in a chemical context, with the goal of producing a “periodic table of planets”. Additionally, the outputs from this team will be critical inputs to other teams modeling the atmospheres of other worlds.

Researchers from Hampton University will be exploring the sources and sinks for volatiles on habitable worlds. The “Living, Breathing Planet Team," led by William B. Moore, will study how the loss of hydrogen and other atmospheric compounds to space has profoundly changed the chemistry and surface conditions of planets in the Solar System and beyond. This research will help determine the past and present habitability of Mars and even Venus, and will form the basis for identifying habitable and eventually living planets around other stars.

The team centered at NASA’s Goddard Institute for Space Studies will investigate habitability on a more local scale. Led by Tony Del Genio, it will examine the habitability of Solar System rocky planets through time, and will use that foundation to inform the detection and characterization of habitable exoplanets in the future.

The NASA Astrobiology Institute's Virtual Planetary Laboratory, based at the University of Washington, was founded in 2001 and is a heritage team of the NExSS network. This research group, led by Dr. Victoria Meadows, will combine expertise from Earth observations, Earth system science, planetary science, and astronomy to explore factors likely to affect the habitability of exoplanets, as well as the remote detectability of global signs of habitability and life.

Five additional teams were chosen from the Planetary Science Division portion of the Exoplanets Research Program (ExRP). Each brings a unique combination of expertise to understand the fundamental origins of exoplanetary systems, through laboratory, observational, and modeling studies.

A group led by Neal Turner at NASA’s Jet Propulsion Laboratory, California Institute of Technology, will work to understand why so many exoplanets orbit close to their stars. Were they born where we find them, or did they form farther out and spiral inward? The team will investigate how the gas and dust close to young stars interact with planets, using computer modeling to go beyond what can be imaged with today's telescopes on the ground and in space.

A team at the University of Wyoming, headed by Hannah Jang-Condell, will explore the evolution of planet formation, modeling disks around young stars that are in the process of forming their planets. Of particular interest are “transitional” disks, which are protostellar disks that appear to have inner holes or regions partially cleared of gas and dust. These inner holes may be caused in part by planets inside or near the holes.

A Penn State University team, led by Eric Ford, will strive to further understand planetary formation by investigating the bulk properties of small transiting planets and implications for their formation.

A second Penn State group, with Jason Wright as principal investigator, will study the atmospheres of giant planets that are transiting hot Jupiters with a novel, high-precision technique called diffuser-assisted photometry. This research aims to enable more detailed characterization of the temperatures, pressures, composition, and variability of exoplanet atmospheres.

The University of Maryland and NASA’s Goddard Space Flight Center team, with Wade Henning at the helm, will study tidal dynamics and orbital evolution of terrestrial class exoplanets. This effort will explore how intense tidal heating, such as the temporary creation of magma oceans, can actually save Earth-sized planets from being ejected during the orbital chaos of early solar systems.

Another University of Maryland project, led by Drake Deming, will leverage a statistical analysis of Kepler data to extract the maximum amount of information concerning the atmospheres of Kepler's planets.

The group led by Hiroshi Imanaka from the SETI Institute will be conducting laboratory investigation of plausible photochemical haze particles in hot, exoplanetary atmospheres.

The Yale University team, headed by Debra Fischer, will design new spectrometers with the stability to reach Earth-detecting precision for nearby stars. The team will also make improvements to Planet Hunters, a web interface that allows citizen scientists to search for transiting planets in the NASA Kepler public archive data. Citizen scientists have found more than 100 planets not previously detected; many of these planets are in the habitable zones of host stars.

A group led by Adam Jensen at the University of Nebraska-Kearney will explore the existence and evolution of exospheres around exoplanets, the outer, ‘unbound’ portion of a planet's atmosphere. This team previously made the first visible light detection of hydrogen absorption from an exoplanet's exosphere, indicating a source of hot, excited hydrogen around the planet. The existence of such hydrogen can potentially tell us about the long-term evolution of a planet's atmosphere, including the effects and interactions of stellar winds and planetary magnetic fields.

From the University of California, Santa Cruz, Jonathan Fortney’s team will investigate how novel statistical methods can be used to extract information from light which is emitted and reflected by planetary atmospheres, in order to understand their atmospheric temperatures and the abundance of molecules.

Image Credit: NASA
Explanation from: http://www.nasa.gov/feature/nasa-s-nexss-coalition-to-lead-search-for-life-on-distant-worlds

Two storm cells over New Mexico

New Mexico, USA

June 2014

Image Credit & Copyright: Camelia Czuchnicki

Sunrise over Pacific Ocean seen from the International Space Station

ISS, Orbit of the Earth

August 2016

Image Credit: NASA/ESA

Panoramic view of Mount Sharp, Mars

This mosaic of images from the Mast Camera (Mastcam) on NASA's Mars rover Curiosity shows Mount Sharp in a white-balanced color adjustment that makes the sky look overly blue but shows the terrain as if under Earth-like lighting. White-balancing helps scientists recognize rock materials based on their experience looking at rocks on Earth. The Martian sky would look more of a butterscotch color to the human eye. White balancing yields an overly blue hue in images that have very little blue information, such as Martian landscapes, because the white balancing tends to overcompensate for the low inherent blue content.

Mount Sharp, also called Aeolis Mons, is a layered mound in the center of Mars' Gale Crater, rising more than 3 miles (5 kilometers) above the crater floor, where Curiosity has been working since the rover's landing in August 2012. Lower slopes of Mount Sharp are the major destination for the mission, though the rover will first spend many more weeks around a location called "Yellowknife Bay," where it has found evidence of a past environment favorable for microbial life.

This mosaic was assembled from dozens of images from the 100-millimeter-focal-length telephoto lens camera mounted on the right side of the Mastcam instrument. The component images were taken during the 45th Martian day, or sol, of Curiosity's mission on Mars (September 20, 2012). The sky has been filled out by extrapolating color and brightness information from the portions of the sky that were captured in images of the terrain.

Image Credit: NASA/JPL-Caltech/MSSS
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA16768

Europe at Night seen from the International Space Station

ISS, Orbit of the Earth

September 2016

Image Credit: NASA/ESA

Mars in Ultraviolet

New global images of Mars from the MAVEN mission show the ultraviolet glow from the Martian atmosphere in unprecedented detail, revealing dynamic, previously invisible behavior. They include the first images of "nightglow" that can be used to show how winds circulate at high altitudes. Additionally, dayside ultraviolet imagery from the spacecraft shows how ozone amounts change over the seasons and how afternoon clouds form over giant Martian volcanoes. The images were taken by the Imaging UltraViolet Spectrograph (IUVS) on the Mars Atmosphere and Volatile Evolution mission (MAVEN).

"MAVEN obtained hundreds of such images in recent months, giving some of the best high-resolution ultraviolet coverage of Mars ever obtained," said Nick Schneider of the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder.

Nightside images show ultraviolet (UV) "nightglow" emission from nitric oxide (abbreviated NO). Nightglow is a common planetary phenomenon in which the sky faintly glows even in the complete absence of external light. Mars' nightside atmosphere emits light in the ultraviolet due to chemical reactions that start on Mars' dayside. Ultraviolet light from the sun breaks down molecules of carbon dioxide and nitrogen, and the resulting atoms are carried around the planet by high-altitude wind patterns that encircle the planet. On the nightside, these winds bring the atoms down to lower altitudes where nitrogen and oxygen atoms collide to form nitric oxide molecules. The recombination releases extra energy, which comes out as ultraviolet light.

Scientists predicted NO nightglow at Mars, and prior missions detected its presence, but MAVEN has returned the first images of this phenomenon in the Martian atmosphere. Splotches and streaks appearing in these images occur where NO recombination is enhanced by winds. Such concentrations are clear evidence of strong irregularities in Mars' high altitude winds and circulation patterns. These winds control how Mars' atmosphere responds to its very strong seasonal cycles. These first images will lead to an improved determination of the circulation patterns that control the behavior of the atmosphere from approximately 37 to 62 miles (about 60 to 100 kilometers) high.

Dayside images show the atmosphere and surface near Mars' south pole in unprecedented ultraviolet detail. They were obtained as spring comes to the southern hemisphere. Ozone is destroyed when water vapor is present, so ozone accumulates in the winter polar region where the water vapor has frozen out of the atmosphere. The images show ozone lasting into spring, indicating that global winds are inhibiting the spread of water vapor from the rest of the planet into winter polar regions. Wave patterns in the images, revealed by UV absorption from ozone concentrations, are critical to understanding the wind patterns, giving scientists an additional means to study the chemistry and global circulation of the atmosphere.

MAVEN observations also show afternoon cloud formation over the four giant volcanoes on Mars, much as clouds form over mountain ranges on Earth. IUVS images of cloud formation are among the best ever taken showing the development of clouds throughout the day. Clouds are a key to understanding a planet's energy balance and water vapor inventory, so these observations will be valuable in understanding the daily and seasonal behavior of the atmosphere.

"MAVEN's elliptical orbit is just right," said Justin Deighan of the University of Colorado, Boulder, who led the observations. "It rises high enough to take a global picture, but still orbits fast enough to get multiple views as Mars rotates over the course of a day."

Image Credit: NASA/MAVEN
Explanation from: https://www.nasa.gov/press-release/goddard/2016/maven-uv-mars

Artist’s impression of exoplanet HD 209458b with comet-like tail

This artist's illustration shows a view of the gas giant planet HD 209458b, as seen from the surface of a hypothetical nearby companion object. The planet is orbiting so close to its sunlike star that its heated atmosphere is escaping into space. Spectroscopic observations by the new Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope suggest that powerful stellar winds are sweeping the castoff material behind the scorched planet and shaping it into a comet-like tail.

Image Credit: NASA, ESA, and G. Bacon (STScI)
Explanation from: https://www.spacetelescope.org/images/opo1021a/

Aurora over Yukon

Yukon, Canada

Image Credit & Copyright: Marc Adamus

Artist's Impression of the view of the Solar System from the surface of Sedna

This is an artist's impression of noontime on Sedna, the farthest known planetoid from the Sun. Over 8 billion miles away, the Sun is reduced to a brilliant pinpoint of light that is 100 times brighter than the full Moon. (The Sun would actually be the angular size of Saturn as seen from Earth, way too small to be resolved with the human eye.) The dim spindle-shaped glow of dust around the Sun defines the ecliptic plane of the solar system where the major planets dwell. To the left, the hazy plane of our Galaxy, the Milky Way, stretches into the sky. The background constellations are Virgo and Libra.

At this distance the Sun's feeble rays are nearly one four-thousandth the intensity of what they are at Earth. This means that Sedna is eternally cold at minus 400 degrees Fahrenheit, which means that the planetoid is airless and icy. Life, as we know it, could never live here. But if anything could survive, it would have an intriguing global view of the entire Solar System. A fifth-magnitude object, barely three degrees from the Sun (the pinpoint at the two o'clock position) is Jupiter. Saturn is also visible as a dim star. Earth would be only half a degree from the Sun and, at ninth magnitude, only be visible in powerful binoculars. To our imaginary "Sednian" astronomers, all the planets would be in inferior orbits (meaning interior to Sedna's orbit). This means they would best be seen in the predawn morning sky and post sunset evening sky, but never at midnight.

Image Credit: NASA, ESA and Adolf Schaller
Explanation from: http://hubblesite.org/newscenter/archive/releases/2004/14/image/e/

NGC 5128: Mysterious Cosmic Objects Erupting in X-rays Discovered

• Two flaring objects in two different galaxies may represent an entirely new phenomenon.

• These objects brighten in X-rays by a factor of 100 in about a minute before returning to previous level in about an hour.

• There are several important differences between these objects and magnetars, which are also known to flare rapidly in X-rays.

• Astronomers used data from both Chandra and XMM-Newton to make this discovery.

This image shows the location of a remarkable source that dramatically flares in X-rays unlike any ever seen. Along with another similar source found in a different galaxy, these objects may represent an entirely new phenomenon.

These two objects were both found in elliptical galaxies, NGC 5128 (also known as Centaurus A) shown here and NGC 4636. In this Chandra X-ray Observatory image of NGC 5128, low, medium, and high-energy X-rays are colored red, green, and blue, and the location of the flaring source is outlined in the box to the lower left.

Both of these mysterious sources flare dramatically - becoming a hundred times brighter in X-rays in about a minute before steadily returning to their original X-ray levels about an hour later. At their X-ray peak, these objects qualify as ultraluminous X-ray sources (ULXs) that give off hundreds to thousands of times more X-rays than typical X-ray binary systems where a star is orbiting a black hole or neutron star.

Five flares were detected from the source located near NGC 5128, which is at a distance of about 12 million light years from Earth. A movie showing the average change in X-rays for the three flares with the most complete Chandra data, covering both the rise and fall, is shown in the inset.

The source associated with the elliptical galaxy NGC 4636, which is located about 47 million light years away, was observed to flare once.

The only other objects known to have such rapid, bright, repeated flares involve young neutron stars such as magnetars, which have extremely powerful magnetic fields. However, these newly flaring sources are found in populations of much older stars. Unlike magnetars, the new flaring sources are likely located in dense stellar environments, one in a globular cluster and the other in a small, compact galaxy.

When they are not flaring, these newly discovered sources appear to be normal binary systems where a black hole or neutron star is pulling material from a companion star similar to the Sun. This indicates that the flares do not significantly disrupt the binary system.

The two objects were both found in elliptical galaxies, NGC 5128 (also known as Centaurus A) shown here and NGC 4636. In this Chandra X-ray Observatory image of NGC 5128, low, medium, and high-energy X-rays are colored red, green, and blue.

While the nature of these flares is unknown, the team has begun to search for answers. One idea is that the flares represent episodes when matter pulled away from a companion star falls rapidly onto a black hole or neutron star. This could happen when the companion makes its closest approach to the compact object in an eccentric orbit. Another explanation could involve matter falling onto an intermediate-mass black hole, with a mass of about 800 times that of the Sun for one source and 80 times that of the Sun for the other.

Image Credit: NASA/CXC/UA/J.Irwin et al.
Explanation from: http://chandra.harvard.edu/photo/2016/ngc5128/

Cat Island

Tashirojima is a small island in Ishinomaki, Miyagi, Japan. It lies in the Pacific Ocean off the Oshika Peninsula, to the west of Ajishima. It is an inhabited island, although the population is quite small (around 100 people). It has become known as "Cat Island" due to the large stray cat population that thrives as a result of the local belief that feeding cats will bring wealth and good fortune. The cat population is now larger than the human population on the island. There are no pet dogs on the island due to the large cat population.

The island is divided into two villages/ports: Oodomari and Nitoda. Ajishima, a neighbouring island, used to belong to the town of Oshika, while Tashirojima was a part of the city of Ishinomaki. On April 1, 2005, Oshika merged with Ishinomaki, so now both islands are a part of Ishinomaki.

Since 83% of the population is classified as elderly, the island's villages have been designated as a "terminal village" which means that with 50% or more of the population being over 65 years of age, the survival of the villages is threatened. The majority of the people who live on the island are involved either in fishing or hospitality.

The island is also known as Manga Island, as Shotaro Ishinomori built manga-related buildings on the island, resembling a cat.

In Japan's late Edo Period, much of the island raised silk-worms for their textiles. The residents kept cats to chase the mice away from their precious silk-worms. As of today, the feral cat population outnumbers humans 6 to 1 on this small Japanese Island.

However, the residents and thousands of tourists who flock to Tashirojima every year do not mind being outnumbered by their feline friends. In Japanese culture, the cat is considered a good luck charm, said to bring money and good fortune to all who cross their path.

Explanation from: https://en.wikipedia.org/wiki/Tashirojima

Artist's Impression of the Surface of Pluto

Just how dim is the sunlight on Pluto, some three billion miles away? This artist's concept of the frosty surface of Pluto with Charon and our Sun as backdrops illustrates that while sunlight is much weaker than it is here on Earth, it isn't as dark as you might expect. In fact, you could read a book on the surface of Pluto.

Image Credit: NASA/Southwest Research Institute/Alex Parker
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA19682

Cloudy Nights, Sunny Days on Distant Hot Jupiters

The weather forecast for faraway, blistering planets called "hot Jupiters" might go something like this: Cloudy nights and sunny days, with a high of 2,400 degrees Fahrenheit (about 1,300 degrees Celsius, or 1,600 Kelvin).

These mysterious worlds are too far away for us to see clouds in their atmospheres. But a recent study using NASA's Kepler space telescope and computer modeling techniques finds clues to where such clouds might gather and what they're likely made of.

Hot Jupiters, among the first of the thousands of exoplanets (planets outside our solar system) discovered in our galaxy so far, orbit their stars so tightly that they are perpetually charbroiled. And while that might discourage galactic vacationers, the study represents a significant advance in understanding the structure of alien atmospheres.

Endless days, endless nights

Hot Jupiters are tidally locked, meaning one side of the planet always faces its sun and the other is in permanent darkness. In most cases, the "dayside" would be largely cloud-free and the "nightside" heavily clouded, leaving partly cloudy skies for the zone in between, the study shows.

"The cloud formation is very different from what we know in the solar system," said Vivien Parmentier, a NASA Sagan Fellow and postdoctoral researcher at the University of Arizona, Tucson, who was the lead author of the study.

A "year" on such a planet can be only a few Earth days long, the time the planet takes to whip once around its star. On a "cooler" hot Jupiter, temperatures of, say, 2,400 degrees Fahrenheit might prevail.

But the extreme conditions on hot Jupiters worked to the scientists’ advantage.

"The day-night radiation contrast is, in fact, easy to model," Parmentier said. “[The hot Jupiters] are much easier to model than Jupiter itself."

An eclipse, then blips

The scientists first created a variety of idealized hot Jupiters using global circulation models -- simpler versions of the type of computer models used to simulate Earth’s climate.

Then they compared the models to the light Kepler detected from real hot Jupiters. Kepler, which is now operating in its K2 mission, was designed to register the extremely tiny dip in starlight when a planet passes in front of its star, which is called a "transit." But in this case, researchers focused on the planets' "phase curves," or changes in light as the planet passes through phases, like Earth’s moon.

Matching the modeled hot Jupiters to phase curves from real hot Jupiters revealed which curves were caused by the planet’s heat, and which by light reflected by clouds in its atmosphere. By combining Kepler data with computer models, scientists were able to infer global cloud patterns on these distant worlds for the first time.

The new cloud view allowed the team to draw conclusions about wind and temperature differences on the hot Jupiters they studied. Just before the hotter planets passed behind their stars -- in a kind of eclipse -- a blip in the planet’s optical light curve revealed a "hot spot" on the planet’s eastern side.

And on cooler eclipsing planets, a blip was seen just after the planet re-emerged on the other side of the star, this time on the planet’s western side.

The early blip on hotter worlds reveals that powerful winds were pushing the hottest, cloud-free part of the atmosphere, normally found directly beneath its sun, to the east. Meanwhile, on cooler worlds, clouds could bunch up and reflect more light on the "colder," western side of the planet, causing the post-eclipse blip.

"We’re claiming that the west side of the planet’s dayside is more cloudy than the east side," Parmentier said.

While the puzzling pattern has been seen before, this research was the first to study all the hot Jupiters showing this behavior.

This led to another first. By figuring out how clouds are distributed, which is intimately tied to the planet’s overall temperature, scientists were able to determine what the clouds were probably made of.

Just add manganese, and stir

Hot Jupiters are far too hot for water-vapor clouds like those on Earth. Instead, clouds on these planets are likely formed as exotic vapors condense to form minerals, chemical compounds like aluminum oxide, or even metals, like iron.

The science team found that manganese sulfide clouds probably dominate on "cooler" hot Jupiters, while silicate clouds prevail at higher temperatures. On these planets, the silicates likely "rain out" into the planet’s interior, vanishing from the observable atmosphere.

In other words, a planet’s average temperature, which depends on its distance from its star, governs the kinds of clouds that can form. That leads to different planets forming different types of clouds.

"Cloud composition changes with planet temperature," Parmentier said. "The offsetting light curves tell the tale of cloud composition. It’s super interesting, because cloud composition is very hard to get otherwise."

The new results also show that clouds are not evenly distributed on hot Jupiters, echoing previous findings from NASA’s Spitzer Space Telescope suggesting that different parts of hot Jupiters have vastly different temperatures.

The new findings come as we mark the 21st anniversary of exoplanet hunting. On Oct. 6, 1995, a Swiss team announced the discovery of 51 Pegasi b, a hot Jupiter that was the first planet to be confirmed in orbit around a sun-like star. Parmentier and his team hope their revelations about the clouds on hot Jupiters could bring more detailed understanding of hot Jupiter atmospheres and their chemistry, a major goal of exoplanet atmospheric studies.

Image Credit: NASA/JPL-Caltech/University of Arizona/V. Parmentier
Explanation from: https://www.nasa.gov/feature/jpl/cloudy-nights-sunny-days-on-distant-hot-jupiters

Earth and Solar Arrays of the International Space Station

ISS, Orbit of the Earth

September 2016

Image Credit: NASA/ESA

Typhoon Lionrock seen from the International Space Station

ISS, Orbit of the Earth

August 2016

Image Credit: NASA/ESA