Astrobiology

Methane Discovered in Exoplanet Atmosphere

Matt Daniels — Thu, 20 Mar 2008 15:11:31 -0700

Description

Researchers report in tomorrow's issue of Nature that a 40-minute gaze with the Hubble Space Telescope last May [2007] has revealed methane in the atmosphere of HD 189733b, a Jupiter-size planet orbiting close to its very bright parent star located 63 light-years away. The observation also confirmed last year's discovery by the Spitzer Space Telescope of water vapor in the planet's atmosphere (see: ScienceNOW, 11 July 2007).

ESA calls this a breakthrough [that] is an important step in eventually identifying signs of life on a planet outside our Solar System.

Science/AAAS News:

Astronomers have detected the organic molecule methane in the atmosphere of an extrasolar planet for the first time and have confirmed earlier observations of water vapor. Alas, the findings don't come close to suggesting that life has emerged on this other world, but they do contribute to a growing body of data about planetary evolution outside our own solar system.

Co-author Mark Swain of NASA's Jet Propulsion Laboratory in Pasadena, California, emphasized that HD 189733b is far too hot--average atmospheric temperature about 1000°C--to support life as we know it. But the presence of methane raises intriguing questions, he said, because the high temperature should have sequestered all of the carbon in the planet's atmosphere in the form of carbon monoxide (CO), not methane (CH4). That suggests a currently unknown chemical process is at work, he said.

Physics & Space Science

Source

http://sciencenow.sciencemag.org/cgi/content/full/2008/319/2

http://www.esa.int/esaSC/SEMTZ1N5NDF_index_0.html

Using satellites to comb for exoplanets and earth-like worlds

Matt Daniels — Tue, 04 Dec 2007 14:36:57 -0800

Description

An extrasolar planet, or exoplanet, is a planet outside our Solar System. Although evidence for 268 planets has been found around 260 other stars (as of December, 2007)[1], so far no one has been able to get a good look at any of them. The study of planets orbiting other stars is one of the most exciting areas of astrophysics today. Most exoplanets have been detected so far through 'indirect' observation -- spectroscopy measurements of parent stars which indicate planetary motion-induced "wobbling" -- rather than direct observation.

With a critical mass of theorists and attention in this area, satellite missions are being planned to find more planets that transit in front of their parent stars (from our vantage point) and enable astronomers to collect unusually rich data on their mass, atmosphere and other features. Transiting planets in particular yield a wealth of information: the depth of the dip in the light curve gives the size of the planet, and the fact that the orbit must be edge-on nails down the actual mass. Together the mass and radius yield the density and surface gravity. Spectroscopy during transit can provide information about the composition of the atmosphere. For only fourteen exoplanet candidates, a slight drop in the light from the parent star has been detected, indicating that the companion is actually a planet[2]. One planned mission, the Transiting Exoplanet Survey Satellite (TESS), hopes to locate as many as a thousand such 'transiting' systems -- these could be followed up on for more detailed study by later space telescopes.

Many think the field of exoplanet observation will progress quickly as a multitude of new projects push the technological envelope. For the first 'image' though, at least one person is willing to make a prediction:
"I think we are very close to having a picture of an exoplanet - maybe even within two years ... it's a race." (Ben Oppenheimer, American Museum of Natural History in New York) [3].
This may be a bit optimistic (depending on whom you talk to), but it is at least indicative of the rate at which the field is advancing.

Primary methods for detecting extrasolar planets:

Doppler spectroscopy ("wobble method"): Measures slight changes in position of star due to planetary orbit. Changes in direction can be detected by measuring the location of spectral emission lines in the star's light. By far the most successful method for detecting the effects of exoplanets.

Astrometry: Detecting similar movement of a star, using precise knowledge of background stars for reference.

Transit method: Measuring a dip in relative luminosity of a star as a planet (presumably) passes in front of the star.

Optical detection: Directly observing a planet, using a coronograph or interferometric methods to diminish the star's light.

The greatest impact: significantly increased fundamental understanding of planetary systems

Key questions that might be impacted:
Are terrestrial planets common or rare?
What are their sizes & distances?
How often are they in the Habitable Zone?
What are their dependencies on stellar properties?

Habitable Zone

[1] NASA Planet Quest

[2] Transiting Exoplanet Survey Satellite (TESS) information sheet.

[3] "Instrument to Unveil New Worlds by Blocking Out Starlight," NASA Lyot Project

[4] Wikipedia, Extrasolar Planets

[5] The first paper: Campbell, B.; Walker, G. A. H.; Yang, S. (1988). "A search for substellar companions to solar-type stars". Astrophysical Journal, Part 1 331: 902 – 921.

Signals

Instrument to Unveil New Worlds by Blocking Out Starlight

PlanetQuest: Exoplanet Exploration

Future of unmanned space exploration

Alex Soojung-Kim Pang — Tue, 23 Oct 2007 11:10:29 -0700

Description

[Revising...]

Improvement in the utility per kg for systems on robotic spacecraft make them increasingly attractive to space agencies for increasing numbers and types of missions.

Even as NASA concentrates its resources on manned lunar and Martian expeditions, unmanned space exploration may find new prominence and greater funding in an effort to replace more costly, less productive science performed on manned missions.

Though ESA's budget ($3.8 billion for FY2005) is roughly a quarter of NASA's ($16 billion for FY2006), ESA's agility and relative lack of legacy programs will help it to achieve more with less funding. Over the coming decade, ESA has concrete plans for unmanned missions to Venus, Mars, Mercury, and in conjunction with the Indian space agency, the moon. ESA will probably use knowledge developed in these programmes, and especially research on new propulsion technologies, to launch even more probes in the years up to 2020 and beyond. Unified platforms and systems of systems will reduce overall costs. Initial probe development promises to beget less expensive probes in the future.

Building upon programmes planned for the 2010 to 2020 timeframe, scientists hope to be able to construct 3D maps of the galaxy, gain a better understanding of the origins of the universe, and search for Earth-like planets. Microsatellites, launched for less than $10 million apiece (for example, Canada's MOST space telescope), will probably play an important role in these discoveries by allowing astronomers more time for otherwise low-priority experiments. Upon its launch around 2011, NASA's James Webb Space Telescope will study the origins of the universe using infrared sensors, if its progress is not hampered by further budget cuts and downsizing.

This will be enabled by:

Expense and inefficiency of scientific experimentation on manned missions

Early indicators include:

Construction by ESA of its Venus Express, using the same platform as the successful Mars Express
Testing of an ion propulsion system by ESA's SMART-1 probe
Wavering by NASA on rehabilitating the Hubble Space Telescope and its lack of planning for a direct replacement
Cutting from NASA's 2006 budget of its Jupiter Icy Moons Orbiter (JIMO), long planned as a testbed for advanced probe technology

What to watch:

An increasing number of scientific papers cite the Hubble Space Telescope rather than the International Space Station.
US cuts funding for deep-space exploration, unmanned programs, and 'blue sky' projects.

Better knowledge of our solar system and those yet unexplored
Potential for discovery of extraterrestrial life
Better understanding of the moments following the Big Bang
Better understanding of the composition and history of Mars, Mercury, and Venus

Signals

Multidisciplinary astrobiology and the quest to find life beyond Earth

Alex Soojung-Kim Pang — Tue, 23 Oct 2007 11:10:29 -0700

Description

[Revising...]

Multidisciplinary efforts by astrobiologists may increase our understanding of the origins of life on this planet and could result in finding biospheres beyond Earth.

Astrobiology, is the study of life in the universe. The field is driven by fundamental questions that have fascinated scientists and lay people for millennia: Where did we come from? Where are we going? Are we alone? Astrobiology is necessarily a multidisciplinary field, drawing from astronomy, genomics, molecular biology, information technology, geology, paleontology, chemistry, physics, astronomy, and planetary science. Through collaborative efforts among these disciplines, scientists hope to understand the origin, evolution, and distribution of life. Astrobiologists start from the assumption that only by dentifying the 'conditions necessary for life to emerge' can scientists know how and where to look for life elsewhere in the universe, especially when habitable environments may be very different from our own home.

Some scientists, notably Jack Cohen and Ian Stewart, reject the term 'astrobiology' and the whole astrobiology programme along with it. For them, talk of 'conditions necessary for life' is both parochial and unimaginative. They dismiss astrobiology as, "the science of Earthlike planets supporting Earthlike life". In place of astrobiology, they speak about 'xenobiology' -- a science that restricts itself less than astrobiology, does not presume to be able to determine the conditions necessary for life and absolutely refuses to discuss 'habitable zones' (regions around stars that are conducive to Earth-type life -- not to hot nor too cold). In general use, the terms are interchangable, but the existence of an emerging coherent field (astrobiology) and a radical opposition to the growing consensus (xenobiology) is significant.

Because scientists have yet to prove the existence of life on other planets, most astrobiology is done on Earth. For example, researchers have been surprised to find life in such extreme environments as incredibly hot volcanic vents in the deep ocean, icy Antarctic lakes, and highly acidic water. These are the kinds of environments that may harbour life elsewhere in the universe, and studying life forms that thrive there opens our eyes to the robustness and adaptability of life. The search for life in the universe continues in biology laboratories too. All life we know about has a similar biochemical basis but it is currently unknown if DNA, etc. is a necessary condition for all life, or just an 'accident' of life on Earth. Attempts to create synthetic life forms will help answer this question. Advances in theoretical biology precipitated by new mathematical approaches are also helping to set the parameters for the search for life beyond Earth.

In our own solar system, scientists have found evidence of water on both Mars and Jupiter's moon Europa. The existence of water is a necessary condition of all life we know, so locations with water may be a good place to start the search for life. In the coming decades, astrobiologists may very well determine whether life exists there or did in the past. Meanwhile, astronomers continue to discover planets outside our solar system, and one of their goals is to find Earth-like planets with chemistry conducive to life as we know it.

The NASA Astrobiology Roadmap outlines seven scientific goals that are expected to be the most fertile ground for exploration in the coming years:

Understand the nature and distribution of habitable environments in the universe
Explore for past or present habitable environments, prebiotic chemistry, and signs of life elsewhere in our solar system
Understand how life originates from cosmic and planetary precursors
Understand how past life on Earth interacted with its changing planetary and solar system environment
Understand the evolutionary mechanisms and environmental limits of life
Understand the principles that will shape the future of life, both on Earth and beyond
Determine how to recognize signatures of life on other worlds and on early Earth

This will be enabled by:

Continued fostering of multidisciplinary science projects
Renewed interest in space exploration, driven by a desire to know if there's life 'out there'
Development of new biological, chemical, and geological tools for analysing samples brought back from space and extreme environments
Development of increasingly advanced telescopes, both terrestrial and space-based
Advances in A-Life that inform theoretical biology
Development of in the laboratory of synthetic micro-organisms
Development of synthetic organisms that use a mechanism other than DNA or RNA to encode information for reproduction

Early indicators include:

1977 discovery of life in hydrothermal vents
Development by James Lovelock of the Gaia Hypothesis from an attempt to determine if there was life on Mars by studying the planet's atmosphere
Discovery of more than 150 exoplanets
Discovery of evidence of liquid water on Europa and possibly Mars
Ongoing development of plans for a manned mission to Mars before midcentury
Founding in 1998 by US NASA of the NASA Astrobiology Institute (NAI), consisting of hundreds of astrobiologists at more than a dozen institutions around the US, from UC Berkeley to Pennsylvania State University to the SETI Institute
Launching of similar large-scale efforts around the world through such NASA partners as the Astrobiology Society of Britain, Australian Centre for Astrobiology, and the Centro de Astrobiologia
Founding of the International Journal of Astrobiology at Cambridge University
Development of A-life (simulated organisms that live in virtual environments)
Application of cellular automata to theoretical biology

What to watch:

New terrestrial planets like Mars and Earth are discovered.

Potential to discover extraterrestial life
Better understanding of the origins of life on Earth, past extinctions, and the possible future of life on this planet
Better understanding of the impact of space environments on human physiology and our own possible future in space
Potential for medical applications of astrobiology tools such as lab-on-a-chip and other bio-assays