More on the search for signs of extraterrestrial life



Yesterday I reported on a workshop held a few months ago on how to search for signs of extraterrestrial life.

Today I’ll report on some other workshops and meetings in recent months that have addressed the same topic, one way or another. The National Academies’ Space Studies Board Committee on Astrobiology and Planetary Science (CAPS) received briefings on these activities yesterday.

The gist of yesterday’s discussions is that as time goes on, planetary exploration (inside and outside our solar system) is becoming more and more focused on looking for habitable environments and signs of extraterrestrial life. Not that we know everything we need to know about planets in our solar system and in other star systems – but it looks like the search for ET life is what will be driving planetary exploration over the next several decades (or more).

Steve Mackwell, corporate director of science programs for the Universities Space Research Association (USRA), reported to CAPS on a “Planetary Science Vision 2050” workshop held at NASA headquarters last month. “Where do we come from? Are we alone, are we unusual? Where are we going” were the threads that knit together discussions at the workshop, Mackwell said.

“Life” turned out to be a major theme of the workshop, he said – to such an extent that it “is an understatement” to say that some members of the planetary science community are concerned that a disproportionate amount of NASA’s science funding – both for missions and for research and analysis – could be devoted to the search for ET life.

Amy Simon, a senior scientist in the Solar System Exploration Division at NASA Goddard Space Flight Center, briefed CAPS on NASA’s Ice Giant Mission Science Definition Team activities. This group has been studying concepts for missions to Uranus and Neptune.

These two ice giants are largely unexplored. (NASA’s Voyager 2 spacecraft flew by Uranus in 1986 and by Neptune in 1989.) They are not only different from the gas giants Jupiter and Saturn but also different from each other. The SDT agrees that “both are equally important” to study, Simon said. “Ideally you’d do a mission to both,” but the cost of such a mission would be high.

(NASA’s already planning an orbiter mission to Jupiter’s moon Europa (Europa Clipper, and NASA’s Europa Lander Science Definition Team issued its report last month.)

Jim Kasting reported on the Space Studies Board’s workshop on “searching for life across space and time,” which I wrote about in yesterday’s blog post.

Mary Voytek, NASA’s senior scientist for astrobiology, told CAPS about a proposed SSB follow-on study of the search for life in the universe: “astrobiology science strategy and the current state of extraterrestrial life detection.”

Voytek explained that the fiscal year 2017 NASA authorization bill, signed into law last week, directs NASA’s Science Mission Directorate to:

  • Task the National Academies with developing a strategy for the study and exploration of extrasolar planets and delivering it to Congress by September 2018 (Section 508).
  • Report to Congress by September 2017 on how NASA plans to expand public-private partnerships in astrobiology (Section 510).
  • Task the National Academies with developing a science strategy for astrobiology and delivering it to Congress by September 2018 (Section 509).
    • NASA’s charge to the National Academies for this latter project reads: “In preparation for the upcoming decadal surveys in astronomy and astrophysics and planetary science, the National Academy of Sciences will appoint an ad hoc committee to carry out a study of the state of the science of astrobiology as it relates to the search for life in the solar system and extrasolar planetary systems.”
    • This study will “outline key scientific and technology challenges in astrobiology particularly as they pertain to the search for life in the Solar System and extrasolar planetary systems; should accommodate the overlap with the Exoplanet Exploration study in the area of assessing habitability and search for signs of life; identify the most promising research goals in the field of life detection in which progress is likely in the next 20 years; consider the role of…partnerships in furthering the to study life’s origin, evolution, distribution, and future in the universe [and how to expand partnerships]; indicate the extent to which U.S. and international missions and telescopes in operation or in development address the key research goals; and make recommendations on the above as appropriate.”
      • (LB note: IMHO this is a huge task to accomplish in 18 months. Good luck!)
      • (Another note: In 2001, the SSB issued a report on a 2000 workshop on life detection techniques. In 2002, it published a report on its examination of U.S. and international programs in astrobiology. In 2005, it published a report on the astrophysical context for life. You can find these reports here. With so much progress made in these areas over the past 10-15 years, it’s time for some updates.)

The NASA astrobiology program published a science strategy in 2015, developed in consultation with about 800 members of the science community. As noted in the charge detailed above, the new National Academies strategy will build on the 2015 strategy. It also will take into consideration the results of several other workshops and initiatives:

  • An exoplanet biosignatures workshop held in July 2016.
  • A meeting hosted at NASA headquarters September 7-9, 2016, “Agnostic biosignatures: recognizing life as we don’t know it.”
  • A workshop hosted by NASA Goddard Space Flight Center, September 12-14, 2016, “Biosignatures of extant life on ocean worlds.”
  • The SSB’s December workshop, “Searching for life across space and time.”
  • The Europa Lander Science Definition Team report published last month.
  • The NASA Ocean Worlds Exploration Roadmap, developed by NASA’s Outer Planets Assessment Group (forthcoming this year).
  • NASA’s Nexus for Exoplanet System Science (NExSS) initiative, established in 2015.

The timeline for producing the new astrobiology strategy , Voytek said, is:

  • April – June 2017 – Engagement with National Academies, negotiation of study terms, establishment of contract.
  • June 2017 – June 2018 – conduct of Astrobiology Strategy Study.
  • June – September 2018 – draft study report, peer review as deemed appropriate, submission of report to NASA.
  • September 2018 – NASA submits report to Congress.

When I think about all the work going on in the planetary science community, the same thoughts run through my mind: so much talent, so many good ideas, so many science questions to answer, so limited the budget. (And today I’m thinking that the humongous addition proposed by the White House this year to the already-super-humongous Defense Department budget could fund a Europa lander, a Uranus orbiter-probe, a Neptune orbiter-probe, a space-based near-Earth object survey telescope, a mission to Venus, a Mars sample return mission including ground-based sample return facility, and then some. Sigh.)

In closing, I’d like to mention a new book written by two genius scientists, D. Eric Smith, a member of the faculty at the Santa Fe Institute, and biologist Harold J. Morowitz (b. 1927-d. 2016): The Origin and Nature of Life on Earth: The Emergence of the Fourth Geosphere (Cambridge University Press, 2016).

According to Amazon: “Uniting the conceptual foundations of the physical sciences and biology, this groundbreaking multidisciplinary book explores the origin of life as a planetary process. Combining geology, geochemistry, biochemistry, microbiology, evolution and statistical physics to create an inclusive picture of the living state, the authors develop the argument that the emergence of life was a necessary cascade of non-equilibrium phase transitions that opened new channels for chemical energy flow on Earth. This…book…provides a well-ordered and accessible introduction to multiple literatures outside the confines of disciplinary specializations, as well as including an extensive bibliography to provide context and further reading. For researchers, professionals entering the field or specialists looking for a coherent overview, this text brings together diverse perspectives to form a unified picture of the origin of life and the ongoing organization of the biosphere.”

I’m familiar enough with the work of the authors to say that they’re both deep thinkers – philosophers of biology, in a way. “The fourth geosphere” is the biosphere. I haven’t read the book yet, but just reading the table of contents gives me an idea of the “deepness” of this book. They write of life as a planetary process, the many forms of order that are fundamental in Earth’s biosphere today, the scales of living processes, the cascade of disequilibria in which stellar and planetary systems operate…and so on…. (You can read the TOC, preface, and epilogue on

Here’s a little sample from their preface:

“For human minds in society, professional disciplines have been the portals to expertise, but the emergency of the biosphere was not a respecter of human silos. Few readers who have spent a lifetime becoming experts in geochemistry, biochemistry, or microbiology will have happened across the fact that the theory of robustness in non-equilibrium systems continues seamlessly to the mathematics of asymptotically optimal error correction. Yet this continuity must have been fundamental to the emergence of hierarchical architecture capable of memory and control over metabolism on the route from minerals to cells.”

Some of us in the astrobiology community like to describe astrobiology as a transdisciplinary field, on beyond inter- or multi-disciplinary, in a sense. As Smith and Morowitz are suggesting, the origin (or origins) and nature of life on Earth are so complex that they cannot be grasped within the boundaries of disciplinary research. For astrobiologists and those who are (like me) deeply interested in it, this book is likely a must-read.



The search for signs of life beyond Earth: gaining ground


This morning, the National Academies’ Space Studies Board Committee on Astrobiology and Planetary Science is receiving a briefing on a workshop last December on searching for life across space and time. I wrote a report on the workshop for posting on It has not been published, so I’m posting it here, with a few updates.

In recent years, NASA planetary missions have identified a growing number of potentially habitable environments in our solar system – planetary bodies that have, or could have, liquid water: Mars, Jupiter’s moons Europa and Ganymede, Saturn’s moons Enceladus and Titan…. NASA’s New Horizons mission gathered evidence that even the dwarf planet Pluto might have a subsurface liquid water ocean. Looking for signs of habitability and life on these bodies, and on planets in other star systems, is now a major focus of NASA’s planetary exploration program.

One of the hottest prospects in the search for evidence of extraterrestrial life in our solar system is Europa, which has a global subsurface liquid water ocean that could be heated by volcanic or hydrothermal activity on the ocean floor.

Last year, responding to congressional direction, NASA established an Ocean Worlds Exploration Program including orbiter and lander missions to the Jovian moon. Planning for a NASA orbiter mission to Europa is already under way. In June, NASA appointed a science definition team (SDT) to identify scientific goals and objectives for a Europa lander mission.

Last month the SDT delivered its report to NASA, identifying three primary goals for this mission, in order of priority: 1) Search for evidence of life on Europa, 2) Assess the habitability of Europa via in situ techniques uniquely available to a landed mission, and 3) Characterize surface and subsurface properties at the scale of the lander to support future exploration. (Two town-hall meetings scheduled this spring – March 19 at the Lunar and Planetary Science Conference in The Woodlands, Texas; and April 23 at the Astrobiology Science Conference in Mesa, Arizona – will provide scientists with an opportunity to comment on this report.)

Given growing interest, inside and outside NASA, in the search for evidence of extraterrestrial life, last year NASA’s Science Mission Directorate tasked the National Academies’ Committee on Astrobiology and Planetary Science with organizing an expert dialogue on “searching for life across space and time.” This dialogue took place in California in December.

“The search for evidence of extraterrestrial life in our solar system and beyond is shifting into high gear. Before we decide where to look for it, we have to pin down what we’re looking for and how we’re going to look for it,” said Mary Voytek, NASA’s senior scientist for astrobiology. “It’s been 15 years since the Academies last reviewed and synthesized the relevant issues in our quest for evidence of extraterrestrial life. The forthcoming report on last month’s workshop will synthesize our current understanding of the limits of life and life’s interactions with planetary environments, as well as of our capabilities to extend this understanding,” said Voytek, who participated in the workshop.

In addition to places, the “time” factor is important to address. As then-NASA Chief Scientist Ellen Stofan noted at the workshop, “A habitable zone is not just a place, it’s a time.”

The aim of the gathering, said workshop chair James Kasting of Pennsylvania State University, was not to produce a consensus or formal recommendations but to gather key people in planetary exploration and exoplanet studies to share ideas.

Questions that drove the dialogue were:

  • What is our current understanding of the limits of life and life’s interactions with the environments of planets and moons?
  • Are we today positioned to design, build and conduct experiments or observations capable of life detection remotely or in situ in our own solar system and from afar on extrasolar worlds?
  • How could targeted research help advance the state of the art for life detection, including instrumentation and precursor research, to successfully address these challenges?

Experts at the workshop considered what exactly “life” is. Is Earth life – life as we know it – the only kind of life that planetary conditions can engender? What does life require? How do life and its environments co-evolve? What does a planetary environment have that life needs? How does life use what its environment has, and how does that use change the environment?

For instance, “are plate tectonics and hydrothermal systems essential to the origin of life?” asked astrobiologist John Baross of the University of Washington. “I would say yes.”

Indications are that astrobiologists are well on the way to life detection in terms of both knowledge and know-how but need more of both.

“The reality is that astrobiology is looking for Earth-like life,” Baross observed. But we also need to be ready for a “surprise,” he said.

As to the search for fossil evidence of past life on Mars, Caltech geologist John Grotzinger, former project scientist for NASA’s Mars Science Laboratory mission, said, “Silica is the great material on Earth that survives everything.” So on Mars, we should be looking to silica deposits for possible evidence.

If astrobiologists ever do find evidence of past life on Mars, given that so much material has been exchanged between Earth and Mars over billions of years (in the form of meteorites), then they will have to determine whether it originated independently of Earth life or whether it’s related to Earth life.

The ocean worlds of our solar system – Europa, Titan, Enceladus, Triton, Ganymede, Callisto, and now Pluto – have subsurface liquid water oceans today, said Jet Propulsion Laboratory astrobiologist Kevin Hand. These ocean worlds offer “the prospect of extant life living in an environment that has not been exposed to Earth (or Martian) life.” Europa’s ocean “has been there for most of the history of the solar system.” In Hand’s judgment, “ocean worlds are possibly the best place to search for extant life” of an independent origin.

As to searching for signs of habitability and life beyond our solar system, exoplanet expert Vikki Meadows of the University of Washington said some important questions to address are, “How could we recognize the effects of life on an extrasolar planet? How do we discriminate life processes from the surrounding environment?” How do we determine false positives and false negatives?” For example, it’s not enough to detect oxygen in an atmosphere. We need to be able to distinguish between biotically and abiotically generated oxygen.

Breakout groups at the workshop addressed these questions: How could targeted research over the next 5-10 years help advance the state of the art for life detection, including instrumentation and precursor research? What do astrobiologists already know and have, and what they need, to work on in-situ detection of life as we know it, in-situ detection of life as we don’t know it (a.k.a. “weird life”), remote detection of life as we know it, and remote detection of life as we don’t know it? Good ideas abounded….

How will these good ideas be translated into good science? NASA Astrobiology has a science strategy in place to guide research over the next decade, and astrobiologists have troves of data to work with from past and current planetary missions. NASA’s Cassini mission to the Saturn system – coming to an end soon, after 12 years of operations – discovered erupting geysers and a global subsurface ocean on Enceladus and revealed Titan as a world with hydrocarbon rain, rivers, lakes and seasons. NASA now has a fleet of spacecraft operating at Mars: the Mars Reconnaissance Orbiter, The Mars Exploration Rover Opportunity, MSL, MAVEN, Mars Odyssey. NASA’s Juno spacecraft is at the Jupiter system, and planning is under way for a dedicated mission to Europa. NASA’s Ocean Worlds Program will work on the best ways to look for evidence of habitability and life on those bodies. At the same time, NASA’s NEXSS project – the Nexus for Exoplanet System Science – is bringing astrobiologists and astrophysicists together in a research coordination network dedicated to the study of planetary habitability. The search for signs of life is definitely on….