Content from the exhibit:Emergence: A New View of Life’s Origin

Introduction

Origin of Life Concepts

The Elements

Formation of the Earth

Timeline

Tree of Life

Extremophiles

Theories

Research

The Scientists

Tableof Contents

Whoever answers this question will have solved one of science’s greatest mysteries. Since groundbreaking experiments performed in the 1950s, researchers have felt they almost had the answer—but not quite. Are we getting close? New research taking place around the globe—including here in New Mexico—suggests we are.

The prevailing origin-of-life theory since the 1950s has been that life emerged through the chance production of a primitive gene out of naturally occurring organic molecules. A new theory, gaining growing support in biological and geological circles, posits that life emerged as a consequence of ordinary chemical reactions that naturally—and perhaps inevitably—led to metabolic reactions. Metabolism is the network of biochemical reactions in cells that provide energy and materials needed to sustain life.

Origin-of-life theories based on metabolism-first are ideal examples of an approach to problem-solving known as complexity science.

Scientific

QuestThe

How & Whydid life on Earth emerge?

Complexity science studies systems and processes as a whole to understand in depth how their parts interconnect and interact. To succeed, researchers from widely diverse disciplines must cooperate closely to share expertise, knowledge, and insights. They use conventional scientific methods such as laboratory experiments and fieldwork, but they depend increasingly on new tools such as advanced mathematical techniques and sophisticated computer modeling.

l

Emergence is critical to complexity science. Emergence refers to processes in which formerly separate components come together and interact to produce new entities of greater complexity. These new entities will have forms and properties not seen in the previously separate parts.

Emergence is one of many processes involved in the evolution of life—contributing innovations and new sources of variation. Evolution combines the constant emergence of these innovations and variations with natural selection, which retains only the variants that are most successful within their environments. Through the combined action of variation and selection, evolution constantly changes the forms and functions of species and ecosystems and can even change the chemistry of the Earth as a whole.

Because its beginning was simple, our universe is primed for increasing complexity. Stars formed when hydrogen atoms were drawn together by gravity. Heavier elements were created in the nuclear furnaces of these stars, and then dispersed into space when the stars exploded. Some of this interstellar material coalesced again, forming new stars and planets, including those in our solar system.

Universe

On Earth, amino acids and other organic molecules were first formed when inorganic molecules interacted. Proteins emerged when amino acids combined and folded into three-dimensional chains. RNA and DNA—the molecules that store and transmit genetic information—formed when sugars provided a means for nucleotides to connect. Fatty acids linked together to encapsulate proteins. These and other processes led to the emergence of cells, the basic unit of life. Multi-cell organisms emerged from the union of single-cell organisms. Plants and animals emerged from these.

The Periodic Table of the Elements might seem like a surprising place to begin searching for clues to life’s origin, but this is exactly where some scientists begin.

Chemical Evolution

An RNA World?

VS

Six Elements Form The Basis Of Life: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur

These elements have been present on Earth since its birth about 4.6 billion years ago. Bonding chemically in various combinations, they form the four kinds of molecules that constitute the building blocks of life—sugars, lipids, amino acids, and nucleobases.

But the Periodic Table contains close to 100 natural occurring elements. Life is not just a product of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Biochemists have long known that trace amounts of Elements 21-30 also play crucial roles in living processes.

Origin of life researchers have noticed that these “transition metals,” which include iron, copper, and nickel, can attach themselves to small molecules (which then become known as “ligands”) and form catalysts for the synthesis of metabolites—essential parts in the network of components that constitute life. This has led some to scientists to hypothesize that transition metal ligand complexes could have served as catalysts in the earliest biochemical pathways.

RNA is a key player not only in the transfer of genetic information, but also in the manufacture of enzymes, the complex molecules used by cells as catalysts today. The discovery suggests to some that early in the history of life, RNA could have performed other crucial functions, including filling the role of catalysts themselves before there were enzymes. This is part of the concept of an “RNA World” in which, among other things, RNA is the bridge between the hypothesized transition metal-based catalysts and enzymes.

1. PROTO-EARTH FORMS as a ball of molten rock from dust, ice, and other materials orbiting the Sun. All the raw materials and energy needed for life are present, but its emergence will have to wait until conditions improve and stabilize.

2. THE PRIMORDIAL PLANET grows larger as it sweeps up planetesimals and other small objects orbiting the Sun. It spins much more rapidly than now: a day lasts only four or five hours.

3. A CATACLySMIC COLLISION with a Mars-sized planet vaporizes Earth’s outer layer and pro-duces a huge cloud of debris that orbits the Earth. The debris coalesces to form the Moon—which, orbiting very close to Earth, produces huge tides and giant storms in newly formed oceans. Giant meteors then pelt the planet, creating clouds of debris that block warmth and light from the Sun.

4. UNDER EARTH’S THIN CRUST, convection currents in molten material known as the mantle produce violent volcanic eruptions. Vast amounts of heat from Earth’s interior are released, and the atmosphere is filled with carbon dioxide.

5. IN THE OCEANS, carbon dioxide from the atmosphere accumulates. It reacts with hydrogen escaping from inside Earth to produce more water—along with methane, acetic acid, and other, more complex molecules essential to life.

6. ON THE OCEAN FLOOR, hydrothermal vents emit steaming-hot water saturated with dis-solved minerals. This leads to the accumulation of other chemicals necessary for life, including nitrogen in the form of ammonia, sulfides, phosphates, and trace amounts of transition metals such as iron, nickel, manganese, cobalt, and zinc.

7. VIOLENT FORCES break the surface of the Earth into tectonic plates, but on the ocean floor, warm sediments and permeable rock (mainly basalt) provide environments where the first living things may emerge to subsist on a diet of inorganic chemicals like the microbial life that flourishes there today.

8. CONTINUING CONVECTION CURRENTS in the mantle generate massive collisions between the tectonic plates. As surface material slides back down into the mantle, portions of the ocean floor are uplifted to form coastal shallows.

9. MOST ORGANISMS taking the ride from the ocean floor to the coastal shallows are killed, but some lucky colonies of bacteria may survive and find themselves positioned perfectly—deep enough to be protected from dangerous solar radiation but shallow enough to use it for energy as the process of photosynthesis evolves. Atmospheric oxygen produced by photosynthesizing bacte-ria over millions of years gives our planet the blue-green cast it has today.

formation of earth

4.6 billion

4.5-4.0 billion

4.5 billion

4.0-3.8 billion

GEOSPHERE

Formation of EarthAs the Proto-Earth cools, it becomes a planet—mostly a hot, turbulent mass of solid, semi-solid, and liquid minerals known as a mantle, with an iron core at the center. At the surface, a thin crust forms, mainly dark-gray to black rock known as basalt.

Formation of MoonCataclysmic collision between Earth and another planet the size of Mars sends a huge cloud of debris into orbit around the Earth. The debris coalesces to form the Moon.

Black EarthThe earth again forms a thin crust above layers of magma. Volcanoes eject gasses that create a new atmosphere and streams of molten magma, or lava, which add to the crust.

Late Heavy BombardmentAsteroids and comets bombard the Earth in record numbers and with overwhelming violence. As the bombardment tapers off, the Earth resumes cooling, oceans reappear, and a crust again covers the planet. Convection currents swirling in the mantle begin to break up the crust and force the pieces to collide, split, and merge.

Origin of Life Timeline

BIOSPHERE

Earth’s first atmosphereHydrogen and helium surround the planet, but are quickly stripped away by intense heat and the solar wind—streams of high-energy particles ejected from the Sun. Asteroids and comets bombard the surface. All the elements necessary for life are present, but it will have to wait until conditions improve and stabilize

Back to Square OneIts new-born crust destroyed, the Earth survives in one piece, sweeps up other debris from the collision, and again begins to cool.

Earth’s Second AtmosphereThe new atmosphere consists of methane, carbon dioxide, water, and other gases. It’s much denser than ours and contains very little free oxygen (O2). Water in the cooling atmosphere condenses into clouds, rains down, and creates vast oceans.

Back to Square One—AgainMuch of the crust melts; the oceans boil away. The atmosphere survives—along, perhaps, with some water inside remnants of the crust.

2.0 billion

3.45 billion

2.7 billion

3.8-3.5 billion

750-570 million

3.5 billion

3.2-1.9 billion

2.5 billion

1.9-1.0 billion

400 million

GEOSPHERE continued

Life EmergesWater from the new oceans seeps through the crust into the circulating magma, to be ejected along with magma at fissures, further breaking up the rocky surface of the crust and initiating chemical reactions leading to new minerals.

First evidence of lifeThe emergence and proliferation of life begins a continuous, never-ending process of change in the chemistry and composition of the atmosphere, the oceans, the ocean floors, and the land. Interactions between organisms and existing minerals will create thousands of new minerals.

Magnetic field formsThe Earth’s iron core begins to generate a permanent but changing magnetic field.

First single cell organismsTectonic processes continue, forming continents as plates permanently merge and creating faults, rifts, ocean trenches, mountain ranges, volcanoes, and thermal vents.

Nitrogen fixationIn the oceans, sulfur and oxygen levels increase, then iron levels decrease. The rise of oxygen makes ammonia unstable, so organisms can no longer rely on geochemistry as a source. They must learn to make their own ammonia—a process known as “nitrogen fixation”—on of evolution’s great innovations. Nitrogen fixation allows organisms to survive the rise of oxygen, to become more independent of geology, and to colonize new environments, eventually including land.

Oxygen generationCyanobacteria began generating oxygen 200 million years earlier, but most of it was absorbed in the oxidation of the iron-rich rock continuously disgorged by volcanoes. Now, volcanic activity diminishes, large continental land masses develop, ocean shallows expand, and cyanobacteria populations explode. Absorption can’t keep up with generation, and oxygen begins to fill the oceans and the atmosphere.

Red Earth: The great oxidation eventRising oxygen levels cause iron and iron-containing minerals in the black basalt to oxidize, turning the Earth’s rocky surface shades of red. Rising oxygen levels also create a layer of ozone (O3) in the upper atmosphere, further blocking ultraviolet solar radiation.

Multicellular organismsExplosive growth in the kinds and numbers of organisms profoundly changes the chemistry of oceans. The era of banded iron and similar formations comes to an end. At around 1.5 billion years, stromatolites find themselves on the brink of extinction.

Snow ball Earth: Recurring Ice AgesRapid fluctuations in the composition of the atmosphere lead to extreme changes in climate, including alternating periods when ice blankets the Earth.

Blue Green Earth: Plants cover the surfaceThe action of plants and fungi breaks down rocks and minerals to create clays and soils.

BIOSPHERE continued

Life Emerges: Date UnknownSingle-cell organisms with complex structures already exist at 3.5 billion years, so the first living things must have emerged earlier. No fossil evidence has been found to tell us when; geologic processes seem to have erased all traces.

First fossil evidence of living creaturesThe earliest organisms likely draw energy from geochemical reactions, only later evolving processes such as photosynthesis—the ability to absorb energy from sunlight and convert it into chemical energy. Only single-cell organisms exist. They will remain the sole form of life for 2 billion years.

Magnetic EarthThe magnetic field begins to deflect high-intensity ultraviolet solar radiation that poses a threat to life.

Energy from lightPhotosynthesis appears, allowing cells to absorb energy from sunlight and convert it into chemical energy. The first photosynthesizers don’t generate oxygen as a by-product and are believed not to use water (H20) but hydrogen sulfide (H2S).

Biochemical processes continue to evolveOrganisms first evolve nitrogen fixation, which many organisms now rely on to produce amino acids.

A critical eventCyanobacteria are the first organisms to produce oxygen as a by-product of photosynthesis. Some cyano-bacteria and their ancestors live in shallow water colonies that form structures called stromatolites—large, layered mats of microbes cemented together by mud.

Earth’s Third AtmosphereRising oxygen levels kill off countless organisms that fail to adapt but open the door to a vast array of new forms of life. Increased protection from the ultraviolet radiation facilitates the evolution of organisms that leave the water and spread across the land.

Multicellular organismsEmerging at an unknown date, they lead to oxygen-based eukaryotes such as the plants and animals we know today. But single-cell organisms are still the most abundant form of life on Earth, thriving in environments once thought too extreme—from deep-ocean thermal vents to arctic ice.

Struggle to surviveGreat numbers of species and ecosystems are driven to extinction. Vast coastal algae blooms come and go as the climate warms and cools. The return to stability ignites the Cambrian Explosion—a momentous period when new organisms appear in great numbers and incredible variety.

The Earth we knowReturn of a relatively warm and stable climate allows plants and animals to flourish and the Earth to evolve into the planet we know today.

Despite life’s diversity, all living things that we know of share the same genetic basis. Whether they come from an amoeba or a zebra, the DNA and RNA are made up of the same chemicals. These chemicals store and transmit information that determines the nature of every living creature. This is called the universal genetic code. Studying this code has become a powerful tool for finding important clues to life’s origin.

Tree of Life

Bacteria Eukaryota Archaea

first cellular organism

inorganics

today

About 3.5-4.3 billion years ago

About 2.7 billion years ago

Bacteria are single-cell organisms that, like archaea, lack a nucleus, the compartment within a cell that separates DNA from the rest of the cell. The most abundant and successful organisms on the planet, bacteria are found everywhere—in soil, in water, in the intestines inside your body.

Bacteria

Branch ActinobacteriaSpecies Unknown

Branch CyanobacteriaSpecies Unknown

Eukaryota differ from bacteria and archaea by possessing a nucleus. Most are microorganisms, but the domain also includes all large complex organisms, including animals, plants, and fungi. The name eukaryote comes from the Greek eu, meaning good or well, and karyon, meaning kernel.

Genetic analysis is refining our understanding of this domain. Eukaryotes are now being organized into genetic supergroups: unikonts (animals, amoebas, and fungi), archaeoplastida (plants and red algae), chromalveolates (alveolates and stramenopiles), and excavates. One of these groups must have been the first to branch off after the formation of the new eukaryotic domain—and thus contain clues to the nature of the eukaryotes’ earliest ancestors—but it’s not yet known which.

Eukaryota

Branch StramenopilesSpecies Diatom

Branch ExcavatesSpecies Giardia

Branch AnimaliaSpecies Opodiphthera eucalypti

Archaea were only shown to be a separate domain—through analysis of their RNA—in 1977. Many archaea thrive under the extreme conditions of hot sulfur pools or in minerals and rock deep inside the Earth. On the floor of the ocean at thermal vents, lacking both sunlight and oxygen, they obtain energy and nutrients from chemical reactions with energetic molecules emerging from the vents and molecules on the mineral surfaces of rocks.

Archaea

Branch MethanobacterialesSpecies M. smithii

Branch MethanococcalesSpecies M. jannaschii

Branch HalobacterialesSpecies Unknown

Making aLiving Cell

How did life on Earth begin? How did a world of inorganic molecules give rise to the first living thing?

No one really knows. There are many uncertainties and controversies. But a general picture is emerging as researchers from diverse fields put together different pieces of the puzzle.

The scenario shown here is based on the metabolism-first theory that cells—the basic units of life on Earth—developed through natural processes along hydrothermal vents on the ocean floor.

MetabolismThe water and rocks around hydrothermal vents on the ocean floor are rich in minerals and chemicals that are known to combine into complex organic molecules—the basic ingredients for the chemistry of life.Heat and chemical energy from the vents mix these organic molecules, producing various sequences of reac-tions, or chemical pathways. If nothing stops them, some of these pathways may run continuously, leading to new pathways that produce amino acids and other biological building blocks.This process could lead to the beginning of metabolism, the chemical reactions that all living things use to pro-duce the energy and components they need to interact with the environment, grow, and reproduce.

CatalysisOur metabolic pathways need special molecules called catalysts to kick off chemical reactions and keep them going. In cells today, catalysts are large, complex molecules called enzymes, but small molecules like iron-sulfur clusters can serve the same purpose in a pre-cellular world. Iron-sulfur surfaces are plentiful around thermal vents, and they could provide the raw materials for these first catalysts.

MemoryHow will these chemical pathways keep going—how will they persist—as they must if they are to lead to life?Today, long sequences of RNA and DNA serve as the memory that preserves and transmits the patterns for these pathways. In our early biochemical world, large molecules like these don’t exist. But early chemical pathways could produce short chains of small molecules that are capable of preserving and transmitting some information. These short chains—named “tiny RNA”—might have been the earliest form of memory that en-abled the pathways to persist.

EncapsulationCells today have complex, active membranes containing walls, pores, and pumps that concentrate their chemi-cal processes and control what comes in and what goes out. How can our simple metabolic pathways protect themselves and control their interactions with the environment before even the simplest cell wall has evolved?The answer could lie in the many small cavities in the rocks around thermal vents. These cavities might pro-vide the protection our developing collection of pathways needs. They may even provide a surface on which a greasy film lining begins to form—this lining could eventually develop some of the capabilities of a cell mem-brane, protecting the collection of pathways and allowing it to interact with the environment outside the cavity.

ReplicationOur pathways and molecules are now enclosed in a membrane and working together. But to create a popula-tion that survives and grows, they need a way to reproduce as a whole. To gain this ability, the tiny RNA will need to evolve until it becomes complex enough to control a long sequence of processes that generates cop-ies of itself.

Replication involves the coordination of all the processes that have been introduced so far—metabolism, catalysis, memory, and encapsulation. When all these processes can be controlled simultaneously, they can be combined into the single action of creating a new cell.

Extremophiles are organisms that thrive in all kinds of extreme environments. They are found throughout New Mexico—on the surfaces of desert rocks, cave walls, lava tubes, and mineshafts. In these environments, scientists have discovered thousands of species of microorganisms whose genes have remained virtually unchanged over billions of years. Going back so far in time, these organisms may harbor important clues to how life originated. This same research into extremophiles is being tapped to help our space program decide what to look for while searching for life on other planets.

-

Origin of LifeTheories

In a 1953 experiment suggested by chemist Harold Urey, graduate student Stanley Miller simulated an atmosphere containing inorganic chemicals thought to have been present on early Earth. To replicate lightning, an electrical charge was passed through this atmosphere. Within a week, a host of simple organic molecules had formed, including amino acids.

The Miller-Urey experiment didn’t show how life on Earth arose; in fact, early Earth conditions were very different from those in the experiment. It did, however, demonstrate that biochemicals necessary for life could arise out of a nonbiochemical stew. The experiment also sparked intense

scientific interest in the origin of life that continues to

this day.

Inspired by Miller-Urey, scientists have conducted extensive research on sugars and nucleobases—the molecules that encode information in DNA and RNA. RNA has drawn a lot of attention: although its function now is to transmit genetic information carried by DNA and to manufacture proteins, many researchers suspect RNA or its precursor was the original carrier of genetic information.

Experiment

A

Since Miller-Urey, the prevailing theory has been that life emerged by chance: powered by lightning or sunlight warming a tidal pool, a group of molecules happened to join together into a complex molecule that could reproduce itself. This set off the chain reaction of reproduction, variation, and evolution that constitutes life on Earth. In the years following the discovery of DNA and RNA, it was hypothesized that an unidentified forerunner to RNA was that first replicating molecule.

The probability that the necessary sequence of chemical reactions to produce this

molecule would occur at any given time was miniscule, but proponents

of the theory thought that, over a span of millions of years, it could have happened.

Was It Chance?

Genes First-

According to the metabolism first theory, life began with the development of metabolic processes out of combinations of naturally occurring chemical reactions. These processes evolved into the chemical pathways and cycles now shared by every living creature. Thermal vents on the ocean floor could have provided the right conditions for this process; archaea and bacteria flourish under these extreme temperatures and pressures.According to this theory, life on Earth may have been inevitable.

Was It Inevitable?

MetabolismFirst

-

Scientists Harold Morowitz and Günter Wächtershäuser, among

others, have homed in on the citric acid cycle and the fact that all living things—without exception

—depend on all or portions of it to metabolize carbon. The citric acid cycle is intriguing for another reason: it

can run in two directions. In oxygen-rich environments like ours, it runs one way and is called the oxidative citric acid

cycle or the Krebs cycle. In oxygen-deprived environments like early Earth, it runs in the opposite direction and is called the reductive citric acid cycle. Some deep-ocean bacteria continue to use this version.

The suspicion is that the reductive citric acid cycle was primordial—that every other biochemical cycle evolved from it. In short, it’s viewed as a strong candidate for the bridge between a non-living and a living planet.

TheCitric

-

Acid

-

There are other, quite different origin-of-life theories. Proponents

of Panspermia suggest that life on Earth—or its essential ingredients—came from outer space. They note that the Murchison meteorite in Australia was found to contain over 90 different amino acids,

including 19 of the 20 deemed essential to life. Even if this theory

explains where life on Earth came from, it still fails to answer how life began before it arrived.

-

Origin of LifeResearch

Lightning is the Earth’s solution to the problem of regulating electrical energy as it builds up in the atmosphere. Hurricanes solve the problem of releasing heat energy that builds up in warm tropical oceans. In the same way, the emergence and evolution of life may be the Earth’s most efficient solution to the problem of dissipating the energy constantly generated inside it.

Ultimately, origin-of-life research could reveal the extent to which the emergence of life and biological processes are governed by universal principles on the order of the laws of motion, gravity, and thermodynamics. It has already provided important insights into how biological systems produce and regulate growth and change.

“What problem with prebiotic Earthwas solved by the emergence of life?”

—D. Eric Smith

Climate affects biology, and biology affects climate. Until recently, models for studying climate change have largely ignored energy flows through biological and ecological systems. Incorporating these interconnections will enhance the models.

While studying life’s origin, Harold Morowitz and his colleague Vijayasarathy Srinivasan stumbled upon a clue to a medical mystery—how Mycobacterium tuberculosis bacteria survive for years inside the human respiratory system, imprisoned by the body’s immune cells and deprived of the oxygen and nutrients they normally depend on.

Two ancient genes possessed by the bacteria may provide the answer. The genes are crucial players in the reductive citric acid cycle, but in the oxygen-rich environment in which the bacteria normally live, only the oxidative citric acid cycle would be needed. Why then have these genes persisted? The answer could be that they’re the organism’s secret weapon, allowing it to switch back to the reductive cycle when trapped inside the body. If correct, this could open new avenues to therapies for tuberculosis and other diseases.

l

Shedding light on the emergence of life on Earth will help us come up with an answer to another question with profound implications: Is there life elsewhere in the universe?

Consider this:

• The building blocks of life are easier to make and more common than once thought.

• Many scientists believe that life emerged on Earth almost immediately once the environment allowed it around 3.8 billion years ago.

• Life forms on Earth have been found to thrive under a wide range of extreme conditions.

• As the number of planets discovered around other stars grows rapidly, it appears increasingly likely that Earth-like conditions, extreme or not, are common throughout the universe.

-

Could this mean that life on Earth and throughout the universe is inevitable?

Meet theScientists

Harold MorowitzHarold Morowitz, a biophysicist at the Santa Fe Institute and George Mason University’s Krasnow Institute, is preparing laboratory experiments to test the catalytic properties of transition metal-ligand complexes common when life began.

Dr. Eric SmithMorowitz’s colleague Dr. Eric Smith is using advanced statistical mathematics and computational modeling to determine the chemical pathways on

early Earth most likely to have led to self-replicating and metabolic processes.

Michael Russell Geochemist Michael Russell, a research scientist in the Planetary Chemistry and As-

trobiology Group at NASA’s Jet Propulsion Laboratory, is investigating the emergence of life and oxygenic photosynthesis in hydrothermal systems on wet, rocky, sunlit planets.

Zaida Luthey-SchultenAt the University of Illinois Urbana-Champaign, Zaida Luthey-Schulten and her group are performing artificial life research that includes computer simulations of ribosomes, the cell’s protein-building machinery; the differences in ribosome structure in the three main branches of the Tree of Life; and their role in the early evolution of protein synthesis.

Robert M. HazenThe role of minerals in the origin of life is the focus of recent research by Earth scientist Robert M. Hazen at George Mason University and the Carnegie Institution’s Geophysics Laboratory.

Steen Rasmussen The goal of other artificial life researchers is to synthesize simple living organisms in the laboratory. At Los Alamos National Laboratory, Steen Rasmussen is attempting to assemble a proto-cell.

Shelley CopleyAt the University of Colorado, with the goal of developing a model for the origin of the genetic code, Shelley Copley and her research group are investigating precisely how RNA may have evolved from early chemical reaction networks.

Carl WoeseAt the University of Illinois Urbana-Champaign, molecular biology and evolution researcher Carl Woese (discoverer of the archaea) worked with physicist Nigel Goldenfeld and colleagues to investigate the role of horizontal gene transfer, or gene sharing, in producing the Universal Genetic Code.

Penny J. BostonPenny J. Boston, a speleologist at the New Mexico Institute of Mining and Technology, is conducting research on the geomicrobiology of caves and mines, astrobiology, and extraterrestrial speleogenesis.

Ariel D. AnbarAriel D. Anbar, a biogeochemist in the School of Earth & Space Exploration and the Department of Chemistry & Biochemistry at Arizona State University, is interested in the past and future evolution of the Earth as a habitable planet and how this can inform the search for inhabited worlds beyond Earth.

George CodyGeorge Cody and colleagues in the Geophysics Laboratory of the Carnegie Institution of Washington, D.C., are performing experiments at high temperatures and pressures on potentially prebiotic chemistry at high temperatures and pressures to see how chemical reactions could have produced the reductive citric acid cycle at thermal vents.

Larry S. CrumplerLarry S. Crumpler, research curator at the New Mexico Museum of Natural History & Science, is studying New Mexico volcanoes as well as geology and volcanism on other planets. He is a member of the Mars Exploration Rover science team.