Kennda Lynch is a postdoctoral researcher in Georgia Tech’s School of Earth and Atmospheric Sciences and has just been featured in season two of Science Matters. She studies ancient lakes on Earth that serve as stand-ins for Mars’s formerly-flooded craters. Lynch’s work helps NASA identify potential landing sites on the red planet.
Thursday, March 28
“Ocean Worlds of the Outer Solar System”
Public Lecture and reception
Dr. Kevin Hand, NASA JPL
Smithgall 117 Lecture Hall, 353 Ferst Drive NW, Atlanta, GA 30313, 6:30pm with reception to follow
Friday, March 29
Topic: Planetary Science and Exploration
Topic: Life Origins and its Detection
Building on the success of the 2018 Astrobiology Colloquium, Georgia Tech Astrobiology and ExplOrigins groups are proud to announce the 2019 Exploration and Origins Colloquium, which will take place on March 28-29, 2019. This is the 2nd annual networking event under the theme of exploring the universe and origins of life.
This year the colloquium is split in two sections: the first section is focused on space exploration technology and planetary science, and the second is oriented toward the chemistry and biology of the origins and the search for life. The event will consist of presentations and talks by early career scientists, i.e. graduate and undergraduate students, and post-doctoral fellows, working in the exciting fields of space and planetary science, engineering and astrobiology across Georgia Tech campus and the greater Atlanta. There will also be plenary lectures given by distinguished members of the global astrobiology community. The objective of this interdisciplinary colloquium is to forge connections across the kinds of research at Georgia Tech straddling the boundaries between technology development and hypothesis testing in the search for life’s beginnings and to explore collaborative ideas among participants. Hence, senior researchers and faculty are also highly encouraged to attend.
Dr. Kevin Peter Hand is a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. His research focuses on the origin, evolution, and distribution of life in the solar system with an emphasis on Jupiter’s moon, Europa. His work involves both theoretical and laboratory research on the physics and chemistry of icy moons in the outer solar system. Hand is the Director of the Ocean Worlds Lab at JPL. He served as co-chair for NASA’s Europa Lander Science Definition team and he is the Project Scientist for the Pre-Phase-A Europa Lander mission. From 2011 to 2016 he served as Deputy Chief Scientist for Solar System Exploration at JPL. He served as a member of the National Academies Committee on Astrobiology and Planetary Sciences. His work has brought him to the Dry Valleys of Antarctica, the sea ice near the North Pole, the depths of the Earth’s oceans, and to the glaciers of Kilimanjaro. Dr. Hand was a scientist onboard James Cameron’s 2012 dive to the bottom of the Mariana Trench, and he was part of a 2003 IMAX expedition to hydrothermal vents in the Atlantic and Pacific oceans. He has made nine dives to the bottom of the ocean. In 2011 he was selected as a National Geographic Explorer. Hand earned his PhD from Stanford University and bachelor’s degrees from Dartmouth College. He was born and raised in Manchester, Vermont.
Professor Walker is an astrobiologist and theoretical physicist at Arizona State University, the Deputy Director of the Beyond Center for Fundamental Concepts in Science, and the Associate Director of the ASU-Santa Fe Institute Center for Biosocial Complex Systems. She is also Co-founder of the astrobiology-themed social website SAGANet.org, and a member of the Board of Directors of Blue Marble Space. Her work centers on in the origin of life and how to find life on other worlds. She is most interested in whether or not there are ‘laws of life’ – related to how information structures the physical world – that could universally describe life here on Earth and on other planets. She is active in public engagement in science, with appearances at the World Science Festival and on “Through the Wormhole” and NPR’s Science Friday
Professor Steffes performed his doctoral research at Stanford University where he concentrated on microwave radio occultation experiments using the Voyager and Mariner spacecraft, with specific interest in microwave absorption in planetary atmospheres. Then, in 1982, he joined the faculty of Georgia Tech and is currently a Professor of Electrical and Computer Engineering. His research focuses on microwave and millimeter-wave remote sensing and radio astronomy and has been sponsored by NASA, the NSF, the SETI Institute and by industry. He has been involved with numerous NASA missions, including Pioneer-Venus, Magellan, the Advanced Communications Technology Satellite (ACTS), the High Resolution Microwave Survey (HRMS), and Juno (Jupiter Polar Orbiter).
Locations:
Kevin Hand Public Lecture “Ocean Worlds of the Outer Solar System”: Smithgall 117 Lecture Hall (Student Services Building), 353 Ferst Drive NW, Atlanta, GA 30313
Keynote and oral presentations will be in the Children’s Health Care of Atlanta Seminar Room (EBB 1005), Krone Engineered Biosystems Building (EBB), 950 Atlantic Drive, NW, Atlanta. GA 30332.
The poster session and networking event will be in held the 1stand 2nd floor atria of the Molecular Science and Engineering Building (MoSE), 901 Atlantic Drive NW, Atlanta, GA 30318.
For all questions, please contact us
We are grateful for funding and support from The Georgia Tech Strategic Plan Action Group (SPAG), the School of Earth and Atmospheric Sciences (EAS), The NSF/NASA Center for Chemical Evolution (CCE), The School of Chemical and Biomolecular Engineering, and the School of Chemistry and Biochemistry.
Continue reading “2019 Explorigins Colloquium”
“AbGradCon (Astrobiology Graduate Conference) provides a unique setting for astrobiologically-inclined graduate students and early career researchers to come together to share their research, collaborate, and network. AbGradCon 2018 marks the 14th year of this conference–each time in a different place and organized by a different group of students, but always with the original charter as a guide.”
“These meetings have been wildly successful both when connected to AbSciCon, and as stand-alone conferences. Since it is organized and attended by only graduate students, post docs, and select undergraduates, AbGradCon is an ideal venue for the next generation of career astrobiologists to form bonds, share ideas, and discuss the issues that will shape the future of the field. Take a look at the AbGradCon 2017 conference website to see what’s happened in the past.”
Taken from official AbGradCon Site.
On September 23, 2017 the Life in the Cosmos symposium was attended by over 100 people.
While the symposium is now behind us, you can view select presentations from the program here.
Among the oldest questions conceived by humans are: What is the origin of life, and does life exist on other worlds? Georgia Tech will host a day-long public Symposium on Astrobiology and Society in Fall 2017 with sessions dedicated respectively to Origin and Evolution of Life on Earth and The Search for Life Beyond our Home Planet. Each session will be rounded out by a half-hour discussion led by a panel of distinguished scientists and humanists. Anticipating discoveries that will alter our very concept of life, astrobiology pushes us to reflect upon the meaning of “creation”, our place in it, and how to accommodate scientifically plausible alternatives to longstanding hypotheses and myths. While astrobiology is often presented to the public as ‘other worldly’, and can easily carry utopian visions of possibility and hope, the force of astrobiology is first and foremost terrestrial. The aura of new worlds reminds us that our cosmic ‘other worldly discoveries’ above all concern the planet on which we live. Analysis of data from vent plumes in our solar system or in Pacific Ocean trenches show the ways our solar system has become a laboratory for better understanding our own planet. The symposium and related interviews with participants will be recorded and provide substrate for a documentary that focuses on how astrobiology drives research across science and the humanities, and sparks open and imaginative discussion about Big Questions, including, What is life? What is the value of different life forms? What is humankind’s destiny?
Over 100 registered for this sold out program.
Keynote
Paul Steffes, Professor, School of Electrical and Computer Engineering, Georgia Tech
“How the Search for Extraterrestrial Intelligence has Evolved in the First Two Decades of the 21st Century”
8:30-9:00
Session A
Chair: Martha Grover, Professor, School of Chemical and Biomolecular Engineering
Nick Hud, Regents Professor, School of Chemistry and Biochemistry, Georgia Tech“Exploring the Origins of Life- From the Bottom Up”
9:00-9:20
Loren Williams, Professor, School of Chemistry and Biochemistry, Georgia Tech
“Exploring the Origins of Life- From the Top Down”
9:20-9:40
Eric Smith, External Professor, Santa Fe Institute
“Making Sense of Evolution in the Light of the Rest of Science”
9:40-10:00
Session B
Chair: Paul Sniegowski, Professor of Biology, University of Pennsylvania
William Ratcliff, Assistant Professor, School of Biological Sciences, Georgia Tech
“Exploring the Origin of Multicellularity through Experimental Evolution”
10:45-11:15
Jennifer Glass, Assistant Professor, School of Earth and Atmospheric Sciences, Georgia Tech
“Small but Mighty– How ‘Good’ Bacteria Transformed our Planet”
11:25-11:45
Shelley Copley, Professor, Department of Molecular, Cellular, and Developmental Biology, Cooperative Institute for Research in Environmental Sciences, UC Boulder
“Closely Related Species Follow Different Evolutionary Trajectories”
Lunch
12:15-1:45
Session C
Chair: Kennda Lynch, Postdoctoral Researcher, School of Earth and Atmospheric Sciences, Georgia Tech
James Wray, Assistant Professor, School of Earth and Atmospheric Sciences, Georgia Tech
“Upcoming Astrobiological Opportunities at Mars”
1:45-2:05
Carol Paty, Associate Professor, School of Earth and Atmospheric Sciences, Georgia Tech
“Searching for Europa’s Hidden Ocean”
2:05-2:25
Amanda Stockton, Assistant Professor, School of Chemistry and Biochemistry, Georgia Tech
“High Impact Chemistry- How to Find Life on Other Planets”
2:25-2:45
Gongjie Li, Junior Fellow, Department of Astronomy, Harvard University
“Searching for Habitable Exoplanets”
2:45-3:15
This full-day event was organized in partnership with the Leadership and Multifaith Program and is co-sponsored by Columbia Theological Seminary. The symposium aims to generate a multifaith discussion among scholars, clergy, community leaders, and students about science, spirituality, and the future of life on earth and elsewhere. Speakers will address this theme from diverse disciplinary perspectives, including cognitive science, religious studies, ecology, ecotheology, ethics, and astrobiology. The symposium will be held on February 17, 2018, at the Candler School of Theology at Emory University, located at 1531 Dickey Drive, Atlanta, GA 30322. Lunch is included, and a short reception will follow the final session. This event is free and open to the public. Registration is required.
Registration & Coffee (8:30 – 9:00 A.M.)
Keynote Address (9:30 A.M. – 10:45 A.M.)
Speaker: Arri Eisen, “What Happens When You Mix Monks, Nuns, and Scientists? The Emory Tibet Science Initiative”
Session 1: Life of the Mind-Body-Spirit (10:45 A.M. -12:15 P.M.)
Lunch (12:15-1:30 P.M.)
Session 2: Life Here on Earth (1:30 – 3:00 P.M.)
Session 3: Life in the Cosmos & Where We Go From Here (3:30 – 5:30 P.M.)
Speakers: Ken Knoespel, Loren Williams, Amanda Stockton, Britney Schmidt, Luju Ojha, Chris Reinhard, Lisa Yaszek
Where do we come from? Does life exist elsewhere in the universe? While the latter may seem like the stuff of 21st century science fiction, both questions have been integral to myriad cultures for millennia. Over the last decades however, research the life and physical sciences has brought these inquiries into the realm of science, and given rise to the field of astrobiology. But what do we know about our origins? And how do we search for life? The first part of this interactive symposium will introduce current scientific thought on the beginnings of our biochemistry, the evolution of our planet as a habitable system, and how we search for signs of life in space. The second half will explore the mutually influential roles science and science fiction, the implications of the discovery of water on Mars, and what life might look like on worlds far different than our own. Audience members are encouraged to come curious and ready with questions about the science and its place in our broader human context.
Where: Georgia Tech TSRB Building Auditorium (Technology Square: 85 5th Street, NW @ Spring and 5th)
When: Thursday, April 12, 2018 at 7:00 pm
Why did we go to the Moon? Why does the Vatican support an astronomical observatory? These questions mask a deeper question: why do individuals choose to spend their lives in pursuit of pure knowledge? The motivation behind our choices, both as individuals and as a society, controls the sorts of science that gets done. It determines the kinds of answers that are found to be satisfying. And ultimately, it affects the way in which we think of ourselves.
Biography: Guy Consolmagno, SJ is a brother in the Roman Catholic Society of Jesus (The Jesuits), working since 1993 as an astronomer and meteorite specialist at the Specola Vaticana (Vatican Observatory), located in the Papal summer gardens outside Rome. Since 2014, he has been president of the Vatican Observatory Foundation, which supports the work of the Observatory and especially its 1.8 meter Vatican Advanced Technology Telescope (VATT) in Arizona. In September of 2015, he was named the Director of the Vatican Observatory by Pope Francis.
Consolmagno’s research explores connections between meteorites, asteroids, and the evolution of small solar system bodies. Along with more than 200 scientific publications, he is the author of a number of popular books, including: The Left Turn at Orion (with Dan Davis), and most recently, Would you Baptize an Extraterrestrial? (with Fr. Paul Mueller, S.J.). He also has hosted space programs for BBC Radio 4, has been interviewed in numerous documentary films, and writes a monthly science column for the British Catholic Magazine, The Tablet.
A native of Detroit, MI, Consolmagno earned two degrees from MIT and a doctorate in planetary sciences from the University of Arizona, was a postdoctoral research fellow at Harvard and MIT, served in the US Peace Corps (Kenya), and taught university physics at Lafayette College before entering the Jesuits in 1989. He has served as the chair of the American Astronomical Society’s Division for Planetary Sciences (AAS/DPS) and on the planetary surfaces nomenclature committee of the International Astronomical Union (IAU). Asteroid “4597 Consolmagno” was named in recognition of his work. In 2014 he won the Carl Sagan Medal for Public Outreach by the AAS/DPS.
Georgia Tech Astrobiology is proud to announce that the 2018 Astrobiology Colloquium will take place on March 30th, 2018. This is a new early career event for the Georgia Tech astrobiology community and will consist of presentations and talks by students (both graduate and undergraduate) and post-doctoral fellows working in astrobiology, space science, and engineering across the Georgia Tech campus and greater Atlanta. There will also be plenary lectures given by distinguished members of the global astrobiology community.Our theme, for what we hope is the inauguration of an annual event is: Exploring Life Origins and the Universe: A Networking Event. As such, in addition to our early career speakers, poster presentations, and our plenary lectures, there will be networking and innovation platform activities to forge connections and explore collaborative ideas among participants. Hence, senior researchers and faculty are highly encouraged to attend.
Registration for the 2018 Georgia Tech Astrobiology Colloquium is now closed as the event has reached capacity. However, an overflow space with a direct feed to the conference presentations is available in the Suddath Symposium Room located on the first floor of the Parker H. Petit Institute for Bioengineering and Bioscience Building (IBB). This room will have a view-only feed from the main colloquium in EBB and is open to the entire campus community. Space is limited and first come-first served.
For colloquium updates and notifications please join our mailing list by clicking here
(Please Note: This is an announcement e-mail list only for updates about the colloquium.)
For all other questions, please contact us
Martha Grover
Glenn Lightsey
Jennifer Glass
March 30, 2018
Translation is one of the most ancient and essential biological processes. An important step in the process is aminoacylation, by which tRNA are loaded with the amino acid cognate to their anticodon specificity. This process is carried out in all life by two unrelated groups of proteins, Class I and Class II aminoacyl-tRNA synthetases (aaRSs), each class containing protein families with specificity for 10 of the 20 canonical amino acids. As all aaRS families are present across all 3 Domains of life, it has been inferred that the lineage containing LUCA inherited a full “modern” collection of aaRS. Therefore, these protein families must have diversified from a common ancestor pre-LUCA. While clearly homologous, extensive structural and sequence divergence within each family makes alignment and phylogenetic reconstruction extremely difficult. Previous phylogenetic reconstructions of pre-LUCA aaRS divergences have therefore only used small highly conserved regions of the proteins associated with the catalytic aminoacylation domain, leading to poorly resolved histories due to an insufficient number of informative sites. Here I present an improved alignment of Class I aaRS proteins, that recovers a much greater number of informative sites, and produces a fully resolved, robust phylogeny. Improved alignment techniques, including structure-based alignments, still consistently mis-align regions of these proteins. Therefore, a careful, site-by-site manually curated alignment was performed, with reference to structural and functional studies in the literature. The resulting phylogeny is distinctly ladderized, permitting a rooting of protein family divergences based on parsimony models for insertion and deletions. Ancestral sequence reconstruction of the root shows that all 20 amino acids were very likely already being incorporated at conserved sites within the ancestor, requiring a “modern” genetic code to predate the origin of cognate aaRS proteins. This result is only possible if the protein-based aaRS system was predated by an earlier aminoacylation coding system, implicating such a process being part of the RNA world. Additionally, we show that the best fitting evolutionary models for these ancient protein divergences resemble those empirically determined from modern proteins, and that our observed phylogeny is unlikely biased by wrongly assuming that an earlier genetic code operated by the same general substitution frequencies. This further supports that not only the amino acid alphabet, but the structure of the genetic code itself may have been similarly modern at this time. Finally, we make the surprising observation that bacterial leucyl-tRNA synthetase underwent a major recombination event early in its history, inserting its proofreading domain to a different region of the protein. Misalignments resulting from this recombination may have further confounded previous attempts at reconstructing the history of this protein family.
The search for life beyond Earth is a major focus of space exploration, both robotic and human. Informed by the molecular biology revolution, exploration of extreme environments, from Earth, to icy moons, and exoplanets, are dramatically transforming our view of life in the universe. We now know that Mars was once habitable and may support life today. We are developing the Search for Extra-Terrestrial Genomes (SETG) to search for life on Mars ancestrally related to us, possibly shared by ancient impact events that transported a billion tons of rock between our worlds. Beyond Mars, we can now seriously consider missions to search for life at Enceladus, or Europa, although it will require transformational mission capabilities including a revolution in autonomy. More broadly, we now have the foundation to understand the limits of our own adaptation to space, and to augment those limits through innovative engineering, both biologically inspired, and biology-based. Building the tools required for a robotic and human future in space, on Mars, and beyond, we can simultaneously advance human health and sustainability on Earth.
Biography: Christopher E. Carr is a Research Scientist in the Department of Earth, Atmospheric and Planetary Sciences at MIT and a Research Fellow in the Massachusetts General Hospital Department of Molecular Biology. After completing dual S.B. degrees in Aero/Astro and Electrical Engineering from MIT, Dr. Carr worked on the Mars Sample Return mission at the Jet Propulsion Laboratory. As an NSF Graduate Research Fellow, Dr. Carr applied bioengineering principles to human adaptation to space, the bioenergetics of movement, and improved space-suit design. He currently serves as the Science PI for the SETG life detection instrument, also relevant to astronaut health, space biotechnology, and field research. He is broadly interested in searching for and expanding the presence of life beyond Earth.
“The Georgia Department of Economic Development and Georgia Tech Center for Space Technology & Research are hosting a one-day symposium at the Georgia Tech Global Learning Center in Atlanta, GA. The symposium is planning a combination of technical presentations, panel discussions and guest speakers to highlight recent innovations in space science and technology.”
Avi has a wide range of research interest, including black holes, the first stars, and the search for extraterrestrial life. Avi is the chair of the Astronomy Department, founding director of the Black Hole Initiative, director of the Institute for Theory and Computation at Harvard university, and he also chairs the Advisory Committee for the Breakthrough Starshot Initiative.
The focus of our work is to determine the constraints placed by atmosphere-water-rock interactions on the environmental conditions for self-assembly of the molecular building blocks of the earliest like-like entities, “protocells.” We have addressed the problem that modern geochemical concentrations of total dissolved phosphate (PT) and Mg2+ are much lower than those are required for non-enzyamtic (prebiotic) RNA synthesis, while Mg2 and Ca2+ concentrations are too high for membrane stability, so how did life emerge on early Earth? We used a geochemical thermodynamic modeling approach, to show that a single, globally-occurring geological process of komatiite rock weathering and evaporation of the resulting solutions under specific partial pressures of atmospheric CO2 (PCO2) can quantitatively provide the PT, Mg2+ and Ca2+ concentrations required for nucleotide synthesis, RNA polymerization and protocell-membrane stability. Conversely, the biologically-required concentrations of PT, Mg2+ and Ca2+ place constraints on the PCO2 levels on early Earth compared to previous estimates ranging over five orders of magnitude. Using these environmental constraints on Mg2+ and Ca2+ concentrations, we examined the stability and evolution of simple protocell membranes from pure single chain amphiphile (SCA) compositions through mixed SCA-phospholipid (PL) to pure PL compositions found in modern cells. We showed that, rather than acting being toxic, the divalent cations promoted evolution of the membranes towards more modern compositions. We also found that RNA oligomer synthesis is possible even at much lower concentrations of Mg2+ than previously reported, well within the concentration range constrained by the atmosphere-water-rock interactions. Thus, we have used a geochemical modeling approach to create the components of a simple protocell under geochemically plausible conditions.
Reception to follow at 4:00 in ES&T L1 Atrium
Earth’s 4.5 billion-year history is a complex tale of deterministic physical and chemical processes, as well as “frozen accidents.” This history is preserved most vividly in mineral species, as explored in new approaches called “mineral evolution” and “mineral ecology.”
This lecture will explore possible roles of mineral surfaces in life’s origins, including molecular synthesis, protection, selection, concentration, and templating. We find that Earth’s changing near-surface mineralogy reflects the co-evolving geosphere and biosphere in a variety of surprising ways that touch on life’s origins. Recent research adds two important insights to this discussion. First, chance versus necessity is an inherently false dichotomy when considering the possibility of life on other worlds—a range of probabilities exists for many natural events. Second, given the astonishing combinatorial chemical richness of early Earth, chemical events that are extremely rare may, nevertheless, be deterministic on time scales of a billion years.
A fundamental goal of mineralogy and petrology is the deep understanding of mineral phase relationships and the consequent spatial and temporal patterns of mineral diversity and distribution in rocks, ore bodies, sediments, meteorites, and other natural polycrystalline materials. Large and growing databases of mineral species, properties, localities, and co-occurrence provide opportunities for data-driven discovery in mineralogy, including the prediction of new mineral species and ore deposits.
Data-driven discovery depends on three key developments: (1) enhanced data resources in mineralogy and petrology; (2) development and implementation of analytical and visualization methods; and (3) creative framing of questions related to mineral diversity, distribution, and co-occurrence in space and time.
We are especially interested in visualization methods that illustrate multiple attributes of complex mineral systems. In particular, network analysis provides a dynamic, quantitative, and predictive visualization framework for employing “big data” to explore complex and otherwise hidden higher-dimensional patterns of diversity and distribution in such mineral systems. Mineral networks (see Figure) facilitate quantitative comparison of lithologies from different planets and moons, analysis of coexistence patterns simultaneously among hundreds of mineral species and their localities, exploration of varied paragenetic modes of mineral groups, and investigation of changing patterns of mineral occurrence through deep time. Mineral network analysis, furthermore, represents an effective visual approach to teaching and learning in mineralogy and petrology.
The attempt to understand how and why Life emerged on Earth has been an approachable scientific question since the 1930s. However, what we think that question is, and what counts as an answer, have continually changed as our understandings of biology and of planetary and space chemistry have repeatedly been overturned. In this talk I will review four approaches to the problem of life’s origin, each anchored in a paradigm-changing discovery about nature but also to some extent reflecting traditional viewpoints from different disciplines. One approach focuses on the molecules of life and how to make them. A second emphasizes the capacity of Darwinian evolution to shape matter, and the particular role of nucleic acids in carrying the evolutionary process on Earth. A third emphasizes the intricate embedding of the biosphere within geochemistry and planetary energetics, and interprets the invariance of these relations over geological timescales as evidence of constraints on the possibilities for both living matter and evolution. The fourth approach, emphasizing the problem of Life’s robustness, is still mostly passed over both in biology and in Origin of Life, but lessons learned in physics about the hierarchy of matter suggest that it is as fundamental as the other three. From each new point of view, the requirements for an explanation of Life’s emergence have changed. Regarding them together, we can arrive at a provisional definition of the nature of the living state that is at once commonsense, but surprisingly far-removed from the definitions that were thought to be adequate a century ago.
Metabolism is the biochemical network that supplies the energy and building blocks for all cells on Earth. The collective metabolism of all cells in turn mediates the global biogeochemical cycles, which regulate Earth’s climate. Reconstructing metabolic evolution provides a powerful lens for linking evolutionary dynamics across levels of biological organization and for understanding the chemical co-evolution of Earth and the biosphere. I will illustrate these ideas using globally abundant oceanic phytoplankton and co-occurring bacteria as a model system. I will argue the macroevolution of this system drew down nutrients in the surface oceans, thereby increasing total ecosystem biomass, while also increasing levels of dissolved organic carbon. I will further argue this evolutionary dynamic produced a collective mutualism in oceanic microbial ecosystems that is highly similar to that of organelles within plant cells. Finally I will argue that the evolutionary self-organization of oceanic microbial ecosystems contributed to the oxygenation of Earth, and more generally that the rise of atmospheric oxygen reflects an increasing metabolic rate of the biosphere.