JWST Will Provide Capability to Search for Biomarkers on Earth-like Worlds

Does another Earth exist somewhere in our galaxy? With the recent lauch of the Kepler spacecraft, astronomers are getting closer and closer to finding an Earth-sized planet in an Earth-like orbit. But once that search succeeds, the next questions driving research will be: Is that planet habitable? Does it have an Earth-like atmosphere? Answering those questions will not be easy. But the telescope up for the task is the James Webb Space Telescope (JWST), set for a planned launch in 2013. Two researchers recently examined the ability of JWST to characterize the atmospheres of hypothetical Earth-like planets, and found this is the telescope that would be able to detect certain gases called biomarkers, such as ozone and methane, for close Earth-size worlds. (See our related article: Q&A with Dr. John Mather on JWST.)

Due to its large mirror and location at the L2 point in outer space, the James Webb Space Telescope will offer astronomers the first real possibility of finding the answers about the habitability of nearby Earth-like worlds, say Lisa Kaltenegger from the Harvard-Smithsonian Center for Astrophysics and Wesley Traub from the Jet Propulsion Laboratory. “We’ll have to be really lucky to decipher an Earth-like planet’s atmosphere during a transit event so that we can tell it is Earth-like,” said Kaltenegger. “We will need to add up many transits to do so – hundreds of them, even for stars as close as 20 light-years away.”

“Even though it’s hard, it will be an incredibly exciting endeavor to characterize a distant planet’s atmosphere,” she added.

In a transit event, a distant, extrasolar planet crosses in front of its star as seen from Earth. As the planet transits, gases in its atmosphere absorb a tiny fraction of the star’s light, leaving fingerprints specific to each gas. By splitting the star’s light into a rainbow of colors or spectrum, astronomers can look for those fingerprints. Kaltenegger and Traub studied whether those fingerprints would be detectable by JWST.

The transit technique is very challenging. If Earth were the size of a basketball, the atmosphere would be as thin as a sheet of paper, so the resulting signal is incredibly tiny. Moreover, this method only works when the planet is in front of its star, and each transit lasts for a few hours at most.

Artists concept of the JWST in space.  Credit: NASA
Artists concept of the JWST in space. Credit: NASA

Kaltenegger and Traub first considered an Earth-like world orbiting a Sun-like star. To get a detectable signal from a single transit, the star and planet would have to be extremely close to Earth. The only Sun-like star close enough is Alpha Centauri A. No such world has been found yet, but technology is only now becoming capable of detecting Earth-sized worlds.

The study also considered planets orbiting red dwarf stars. Such stars, called type M, are the most abundant in the Milky Way – far more common than yellow, type G stars like the Sun. They are also cooler and dimmer than the Sun, as well as smaller, which makes finding an Earth-like planet transiting an M star easier.

An Earth-like world would have to orbit close to a red dwarf to be warm enough for liquid water. As a result, the planet would orbit more quickly and each transit would last a couple of hours to mere minutes. But it would undergo more transits in a given amount of time. Astronomers could improve their chances of detecting the atmosphere by adding the signal from several transits, making red dwarf stars appealing targets because of their more frequent transits.

An Earth-like world orbiting a star like the Sun would undergo a 10-hour transit once every year. Accumulating 100 hours of transit observations would take 10 years. In contrast, an Earth orbiting a mid-sized red dwarf star would undergo a one-hour transit once every 10 days. Accumulating 100 hours of transit observations would take less than three years.

“Nearby red dwarf stars offer the best possibility of detecting biomarkers in a transiting Earth’s atmosphere,” said Kaltenegger.

“Ultimately, direct imaging – studying photons of light from the planet itself – may prove a more powerful method of characterizing the atmosphere of Earth-like worlds than the transit technique,” said Traub.

Direct studies have already been used to create crude temperature maps of extremely hot, giant extrasolar planets. With next-generation instruments, astronomers may be able to study atmospheric compositions, not just temperatures. The characterization of a “pale blue dot” is the next step from there, whether by adding up hundreds of transits of one planet or by blocking out the starlight and analyzing the planet’s light directly.

In a best-case scenario, Alpha Centauri A may turn out to have a transiting Earth-like planet that no one has spotted yet. Then, astronomers would need only a handful of transits to decipher that planet’s atmosphere and possibly confirm the existence of the first twin Earth.

Source: Harvard Center For Astrophysics

19 Replies to “JWST Will Provide Capability to Search for Biomarkers on Earth-like Worlds”

  1. They will find many Earth-type worlds,but most will not be suitable for advanced lifeforms. If any are suitable, perhaps the advanced lifeforms are ‘homebodys’ (no interest in traveling) or extinct, however, if we find a world 50LY away that has lifeforms as advanced and curious as we are, it may take a few thousand years before we know what each other is talking about!!!!!

  2. Nancy,
    With kind respect, I think this article gives the false impression that the sole aim of this telescope is into investigation of search for Earth-like planets. No doubt the capabilities of this new JWST in action will be a significant step up on current technologies in both resolution and plethora of instrumentation available for the astronomer to use.
    IMO, the focus on discovering Earth-like planets and the tell tale signs of life is a very good priority based on perceived popularity among the general public, but it is not overall so in current investigation by astrophysics.
    I think really the top aim, like Hubble, is the distant universe in regions of the first stars, galaxy formation and the processes in which they came to be. Second would be in regards stellar evolution and star creation in nebulae – including formation of galactic solar system. The adept capability of the infra-red instrumentation is equally, if no more so, for these other tasks.
    In reality, the desire to find possible distant Earth would be nice but isn’t as pivotally essential to the science. (Note: I am not saying don’t look for such planets at all, but instead to put the work among the grander picture.)
    After all, I still think it is more interesting how solar systems beyond our own have come to be and the commonness or lack thereof of such systems.

  3. “He [Democritus] said that the ordered worlds are boundless and differ in size, and that in some there is neither sun nor moon, but that in others, both are greater than with us, and yet with others more in number. And that the intervals between the ordered worlds are unequal, here more and there less, and that some increase, others flourish and others decay, and here they come into being and there they are eclipsed. But that they are destroyed by colliding with one another. And that some ordered worlds are bare of animals and plants and all water.” — Hippolytus, priest, Refutation of All Heresies: On Democritus, 2nd century

  4. Hey Oils, Why send us these usaful quotes, eh?

    Let’s see. The introduction of this text says it all…

    “We must not overlook any figment devised by those denominated philosophers among the Greeks. For even their incoherent tenets must be received as worthy of credit, on account of the excessive madness of the heretics; who, from the observance of silence, and from concealing their own ineffable mysteries, have by many been supposed worshippers of God.”
    — Hippolytus, priest, Refutation of All Heresies: On Democritus, 2nd century

    This explains a lot.

    Are you a heretic OilIsMastery ?

    (I.e. Definition: “A person holding an opinion at odds with what is generally accepted.)

    If true, are you mad???

    “We have likewise, on a former occasion, expounded the doctrines of these briefly, not illustrating them with any degree of minuteness, but refuting them in coarse digest; not having considered it requisite to bring to light their secret doctrines, in order that, when we have explained their tenets by enigmas, they, becoming ashamed, lest also, by our divulging their mysteries, we should convict them of atheism, might be induced to desist in some degree from their unreasonable opinion and their profane attempt.” — Hippolytus, priest, Refutation of All Heresies: On Democritus, 2nd century

    This says all about you too slippery Oils.

    According to this, you must be an atheist, then!
    Are you now ashamed?

    “Assigning to each of those who take the lead among philosophers their own peculiar tenets, we shall publicly exhibit these heresiarchs as naked and unseemly.” — Hippolytus, priest, Refutation of All Heresies: On Democritus, 2nd century

    Sound like anyone familiar, eh Oils??


    Thanks for the quoted advice!!

  5. Salacious,

    “Are you a heretic OilIsMastery?”

    According to you I am.

    “Of course, I am a heretic, for I question the neutral state of celestial bodies. There are various tests that could be made. For instance, does Jupiter send radio-noises or not? This can easily be found, if you [Einstein] should wish.” — Immanuel Velikovsky, cosmologist, 1954

    “If true, are you mad???”

    According to Grand Inquisitors like you I am.

  6. If we find a world with an oxygenated atmosphere, I’ll rejoice, for it means life is there. A civilization would be fine, but first things first. One possible find would be an atmosphere with combustion products in it: smoke, ash, carbon monoxide, etc. Right there we’d know we’d found a world with a land biota, including photosynthesizing creatures whose tissues would provide fuel for fire, and which liberate oxygen into their atmosphere — oxygen is necessary for combustion. Lightning is universal, so the combination of fuel + oxygen would frequently give rise to fire, with the application of a handy lightning stroke. I’m not sure how easy it would be to detect such biomarkers, though.

  7. Velikovsky wouldn’t help or save you now!
    Your philosophical mumbo-jumbo methods are now totally exposed. We can now see you just as well with JWST will view the universe.
    According to your logic, I thought you said YOU were the Grand Inquisitor! But if your the Grand Inquisitor holding the reins doing God’s work or his own? Eh?
    Clearly those who defy the current doctrine, as Hippolytus did, are the ones fundamentally with the problem – no us!
    Believing science is faith is why science never work until the natural philosophers were given the decent proverbial kick up the backside.
    I think, instead, your posterior is now going to be red raw very soon by the pasting you are now going to get.
    You shouldn’t have opened the door, as you will be unable to close it.
    Again, thanks for the wonderful quoted advice!!
    (The only true madness I see, is you making such a stumbling blunder. Hope you survive it.)

  8. This should read, especially for Mr. Oils;
    “Believing science is faith is why science never worked until the natural philosophers, and they were given a decent proverbial kick up the backside.”

  9. Salacious, yeah, it bugs me that NASA and, it seems, many academic institutions (I don’t know if it’s the scientists or just the press offoce), seem to think that the best way to get public support is by linking everything to the discovery of extraterrestrial life. The result is then that in response the public think that the search for life is all-important because scientists tell them so.

  10. OK then, back on topic I agree with Salacious that the JWST will doing a whole lot more than analysing extrasolar planets for their atmosphere. But it will still do a lot of this, because as the Kepler telescope has been launched and currently undergoing system checks, it will have 4 years between now and the JWST launch to identify promising extrasolar planets and record their transit periods.

    This will allow scheduled windows of analysis to be planned for JWST against a list of stars, rather than just staring at a section of the sky for periods on end. So it should be very efficient at the task discussed in this article.

  11. Oh, the question of faith again rears it’s ugly head. Why the obsession? I guess I must take a side, after all it’s the most important question that any new poster MUST answer. God….the very word makes you uncomfortable does it not? Well, the only answer that I can really give is, I don’t know. We will find other earths and when we do, we may be tempted to seed them with life. Will we return to check on thier progress? Will we use religion to mask our true identities? mmmm

  12. There is no life on other planets, so JWST is just wasting money, our money.
    We better use that money to fight terrorism.

  13. OilIsMastery:

    “Immanuel Velikovsky, cosmologist,”…. afaik, this should read “Immanuel Velikovsky, psychologist, speculating about cosmology”

  14. Well it’s easy enough when I see something with Salacious or Oills mentioned or written by, I just pass on. What a waste. These discussions (generically speaking) were interesting when I first read them 40 years ago. Now they are repetitious and boring. When will people grow up and realize there are no answers.

  15. Joe, it’s sad, they don’t get out much.

    As for the telescope, I’ll take any and all it has to tell us. I love the way they multitask!

  16. ND,


    “speculating” ?

    Because everyone knows, NO ONE speculates in cosmology!

    It’s an exact infallible apodeictic science and anyone who says otherwise should burn at the stake…:P

  17. Good Gad OilIsMastery
    The “infallible apodeictic science” might be true of many aspects of cosmology – but not all its tenets. I.e. The existence of gravity is not apodeictic at all – whose effect equally applies all time all space throughout the universe.
    This very same misnomer you unwisely generate to create an illusion of superiority. Falsifying observations of nature is one thing, but relying on faith and dodgy out-of-date doctrines with you is the greatest apodeictic fact of all.
    Really you should use the phrase “infallible demonstrable science” more often instead – pointing out that its conclusions are real based on the scientific methods and not by magic. Otherwise, you might as well just examine chicken entrails for all proof or the basis real understanding.
    You act more like an augur than any science-trained person to me. Nah. Calling you a ‘natural philosopher’ was a significant mistake – as you are nothing more than pontificating dogmatic crashing bore. Or am I NOW speculating?
    Proof of the world in not possible in your twisted application of illogical semantics as stated in you uncommon awry appositeness.
    Note: You still have not answered me “if the sun exists” (was it too hard for you, perhaps?)

  18. comment for the picture:
    isn’t that moon a bit to close to the planet 😛
    the author must think a bit better for his next work

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