UH Astrobiology Team Studies Water and Life in the Universe
by Karen Meech and Eric Gaidos
Studies of interstellar clouds such as IC 1396
may teach us about the presence of water molecules
in star-forming environments. Our Sun and planetary
system most likely formed in a very similar
environment. Courtesy Canada-France-Hawaii Telescope/J.-C.
Cuillandre/Coelum. For more images, see http://www.cfht.hawaii.edu/HawaiianStarlight/
How does life begin and evolve? Is there life
elsewhere in the Universe? What is the future
of life on Earth and beyond? Today, NASA's Astrobiology
Institute (NAI) is not only asking these age-old
questions, it is actively seeking answers. In
June 2003, it selected as its first cross-disciplinary
team a group of UH researchers under the direction
of IfA astronomer Karen Meech. This new NAI
Lead Team will investigate the astrophysical,
cosmochemical, geological, and biological processes
that link the history and distribution of life
in the Universe to that of water.
Founded in 1997, NAI is a multidisciplinary virtual research institute headquartered at NASA Ames Research Center in California. It has
16 lead teams distributed across the
United States and a large number of international partners.
We humans, and all life on Earth, are aqueous beings. Our cells are made mostly of a water solution packaged in membranes. The aqueous
chemistry in these cells is responsible
for growth, reproduction, and life. Water's chemical properties and the way it responds to changes in temperature make it an ideal medium for biological activity, so much so that
it is considered essential for recognizable life. Unlike many compounds, water expands upon freezing, and its ice floats, a property that is crucial for the persistence of aquatic
habitats under freezing surface conditions. In addition to its direct role in biology, water is also a predominant determinant in the geology, geochemistry, and climate of our
planet. It influenced structure and early evolution of the solar system itself, aspects of which dictate the habitability of Earth. Water and life are connected on many scales,
from the interstellar medium to microbial habitats, and through many processes, astrophysical, geological, geochemical, and biological.
The University of Hawaii is located in a unique
island setting, and because of this, has developed
several centers of research excellence: the
Institute for Astronomy and the School of Ocean
and Earth Science and Technology (SOEST), which
includes the Hawaii Institute of Geophysics
and Planetology, the Department of Geology and
Geophysics, and the Department of Oceanography.
Our NAI team takes advantage of the UH's Pacific
location, the excellence of these specialized
research units, and UH's unique research facilities
build a new interdisciplinary research and education
framework around this water theme.
Water is the medium in which the chemistry
of all life on Earth takes place. Water is the
habitat in which life first emerged and in which
much of it still thrives. Water has modified
Earth's geology and climate to a degree that
has allowed life to persist to the present epoch.
Cosmically, water is not uniformly abundant,
and its incorporation into Earth-size planets
is not necessarily constant. Water forms in
the interstellar medium and in the denser molecular
clouds that give rise to star-forming regions.
Differences in the relative abundance of elements
and their isotopes, and in the chemical reactions
that take place among the gases the abundance
of water in those regions. Our team will use
the powerful new submillimeter and infrared
facilities on Mauna Kea to quantify the presence
of water ice in the interstellar clouds, and
to characterize and understand the environments
where water exists in space.
Because of the high abundance of water ice in the interstellar medium, water has played a vital role in physical and chemical processes that have led to the formation of
astrobiologically important molecules. UH NAI team members will perform cutting-edge laboratory chemistry experiments to address for the very first time the important questions of
how the basic life ingredients form out of nonliving matter in extraterrestrial environments, such as molecular clouds, and the crucial role that water plays in their formation.
Comet ices preserve a chemical record of this precursor interstellar material, and detailed remote measurements of the hydrogen isotopes in these icy bodies has shown that comets
contributed some, but not all, of the water to Earth's oceans. Comets are also rich in the organic materials that are essential for life on Earth, and team members will investigate the
inventory of both organics and ices in them.
X-ray image of a piece of the Murchison meteorite,
a primitive water-rich early solar system leftover.
This type of meteorite contains a high abundance
of water-bearing minerals and organics, and
could be a source of water in the inner solar
system. Courtesy of S. Krot (HIGP).
We will also use laboratory equipment to study
the minerals in meteorites that formed as a
result of interaction with liquid water early
in the solar system. These minerals preserve
a record of aqueous activity in their parent
bodies that provides information about the abundance
and distribution of water in the primordial
solar nebula. The cosmochemical record in meteorites
shows that a large range of water abundance
existed in the early solar system, perhaps because
of the removal of water from the warm interior
of the primordial nebula. Planets forming from
planetary building blocks from different parts
of the early solar system would have received
different inventories of water. Comet and meteorite
impacts played a role in helping bring this
water not only to Earth, but to our neighboring
planets Venus and Mars as well.
Mars is the planet most resembling Earth. It
contains unambiguous evidence for the activity
of past and present water, and is probably the
most likely to host or have hosted extant or
extinct life. Studies of the history and action
of water on Mars are of great importance
in this regard. Our studies will model the hydrothermal
and low-temperature alteration of crustal minerals
and rocks by water, and team members will combine
this with data from Earth observations and recent
Mars missions to assess its water inventory
and habitability. The detection by the Mars
Global Surveyor of copious ground ice and recently
carved gullylike landforms raises the possibility
that liquid water is close to the surface of
Mars Global Surveyor image of gullies on Mars.
Courtesy of NASA/JPL/Malin Space Science Systems.
Water has been involved in life since its first
appearance on the early Earth. The leading theories
of the origin of life postulate that prebiotic
chemistry occurred in low-temperature aqueous
solutions that were supplied with prebiotic
molecules by atmospheric chemistry, or in the
hydrothermal brines produced by high-temperature
water-rock interactions. The first three billion
years of the drama of life on this planet were
played out entirely in aquatic environments.
Water is also involved in geochemical reactions
that maintain surface conditions permissive
of life. The presence of water significantly
alters the properties of minerals in Earth's
crust and mantle, something crucial to the operation
of plate tectonics. These geologic processes
in turn drive many of the biogeochemical cycles
important to Earth's habitability.
Our team will investigate the water-rock chemistry in the deep oceans and its relation to habitats for life. The reaction between silicate rocks and water, particularly at
high temperatures (for example, at submarine hot springs near mid-ocean ridges), produces aqueous fluids and altered mineral surfaces whose chemical imbalances are potential
energy sources for life. Besides water, life also requires a source of carbon and nutrients, and an environment that is conducive to the propagation of genetic information.
Many aquatic environments on Earth are challenging or "extreme" from the point of view of better understand what may limit the origin and persistence of life in aquatic habitats elsewhere in the Universe. These extreme environments include lava-water interfaces in the Hawaii Volcanoes National Park as the magma from Kilauea flows into the ocean, as well as steam geysers, high-altitude lakes (such as Lake Waiau on Mauna Kea), and field work in volcanically active Iceland. We will focus here on a comparative study of microbial biodiversity and metabolic activity in these extreme aquatic habitats.
Extreme Habitats: Subglacial eruptions in Grimsvotn,
a volcanic caldera beneath the Vatnajokull ice
cap in Iceland. Beneath the 650-foot-thick ice
shelf within the caldera is a habitat for microbial
life. Photo courtesy of O. Sigurdsson (Icelandic
National Energy Authority). This picture appears
on the Bioastronomy 2004 - Habitable Worlds
poster, an international meeting for scientists
in Reykjavik, Iceland (July 12-16, 2004). UH
NAI and IfA are among the sponsors.
We will develop an integrated model of planetary water and its early history on Earth-like planets, which can be used to explore the time-evolution of water on the early Earth,
as well as Earth-size planets whose space environment or composition differs from Earth's. Extraterrestrial aquatic environments may be far more extreme than most encountered on Earth.
Water inventories and cycles on Earth-size planets around other stars may be quite different from our own. Planetary water abundance may be a very sensitive function of the chemistry
in the planet-forming nebula, the water abundance in that nebula, the presence of giant planets, and factors such as ultraviolet radiation from the central star.
The search for life—and water—will expand
outside the solar system with the eventual deployment
of space observatories (such as the NASA Terrestrial
Planet Finder) capable of detecting and characterizing
Earth-size exoplanets and their environments.
Advanced adaptive optics on Mauna Kea and facilities
such as the Keck interferometer (the combined
use of both Keck telescopes) will play a role
in the characterization of the water-bearing
exoplanets. The 30-meter Giant Segmented Mirror
Telescope now in the planning stages will allow
for the detailed study of protoplanetary disks
around stars and the planetary systems forming
in them. It will also enable scientists to see
giant gas planets orbiting other stars and
to do a detailed physical investigation of their
nature, properties, and chemical composition.
By developing and testing models and exploring
the outcomes of alternative scenarios, we seek
to determine what controls the abundance and
distribution of water and hypothetical aqueous
habitats in other planetary systems.
The members of the UH Astrobiology Lead Team,
their affiliations, and areas of expertise are
listed on the team's Web site.
For more information, see Upcoming Astrobiology Events.