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, www.planethunters.org,
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.
Editor: Sarah Loff
