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Keeping an Eye on Io

Suppose for a moment that you have some novel ideas about astrobiology on Io. The idea seems extreme, but there are scientists who argue for the notion, as we’ll see in a moment. In any case, if you wanted to observe Io, how would you go about it? The best solution is a spacecraft, as it was when Voyager 2 sped through the Jupiter system and discovered what tidal effects can do to a small moon. The Galileo probe, despite the failure of its high-gain antenna, was able to send up-close data about both Europa and Io, confirming that the latter’s volcanic activity was 100 times greater than what we experience on Earth. And then there was Cassini’s lovely view.

Image: Gliding past Jupiter at the turn of the millennium, the Cassini spacecraft captured this awe inspiring view of active Io with the largest gas giant as a backdrop, Credit: Cassini Imaging Team, Cassini Project, NASA.

But the Voyagers are now close to leaving the Solar System, while Galileo was sent to its destruction in the clouds of Jupiter back in 2003. Cassini is orbiting Saturn. Today, you’d have to rely on getting instrument time on the Hubble space telescope to follow-up your Io ideas. But we’ve just had word of a new adaptive optics technology that does Hubble one better. In fact, tests at the Large Binocular Telescope in Arizona have shown that the system — First Light Adaptive Optics, or FLAO — delivers image quality more than three times sharper than Hubble while using only one of the LBT’s two 8.4-meter mirrors. Add in the second mirror and this ground-based system is expected to achieve image sharpness fully ten times that of Hubble.

I share the excitement of Simone Esposito, the leader of a team from Italy’s Arcetri Observatory of the Istituto Nazionale di Astrofisica (INAF), which developed the system in collaboration with Steward Observatory (University of Arizona). Says Esposito:

“The results on the first night were so extraordinary that we thought it might be a fluke, but every night since then the adaptive optics have continued to exceed all expectations. These results were achieved using only one of LBT’s mirrors. Imagine the potential when we have adaptive optics on both of LBT’s giant eyes.”

Indeed. Using a secondary mirror that is pliable enough to be manipulated by actuators pushing on 672 magnets on its back, the technology seems to be a breakthrough in adaptive optics, taking us close to the point where we can see through the atmosphere as clearly as if it did not exist. You can see the results below:

Image: A double star as observed with the LBT in standard mode (left), and with the adaptive correction activated (right). Because of atmospheric blurring, the fainter companion of the star cannot be identified in the images taken in standard mode, while it is easily visible when the adaptive module is activated. A third faint star also becomes visible in the upper right part of the frame, thanks to the increased sensitivity of the telescope in adaptive mode. Credit: INAF/University of Arizona.

Life’s Chances on Io

The revolution in ground-based astronomy that adaptive optics continues to foment is nothing short of breathtaking. Meanwhile, let’s back up a bit to that earlier comment about astrobiology and Io. Dirk Schulze-Makuch (Washington State University) made the case for astrobiology on the seemingly hostile world in a paper last year in the Journal of Cosmology. Io’s plasma particle interactions with Jupiter, its lack of a substantial atmosphere and its extreme temperature gradients all argue against life there. Nor do we see impact craters, indicating a malleable surface that is being constantly reformed.

But there is this to be said about the place: It formed in a part of the Solar System where water ice is plentiful and geothermal heat could have made the origin of life possible. We can imagine a scenario where water was lost on the surface and life went deep underground, where both water and carbon dioxide may still be plentiful. Schulze-Makuch’s view:

Geothermal activity and reduced sulfur compounds could still provide microbial life with sufficient energy sources. Particularly, hydrogen sulfide is probably a common compound in Io’s subsurface…. Volcanic activity is prevalent on Io and lava tubes resulting from that activity could present a favorable habitable environment. Microbial growth is common in lava tubes on Earth, independent of location and climate, from ice-volcano interactions in Iceland to hot sand-floored lava tubes in Saudi Arabia. Lava tubes also are the most plausible cave environment for life on Mars… and caves in general are a great model for potential subsurface ecosystems.

Underground microbial life on Io would, then, be protected from low temperatures and shielded from radiation, in an environment with both trapped moisture and nutrients like sulfide and hydrogen sulfide. Schulze-Makuch speculates that sulfur could play a large role here as a potential building block of life, noting that there is no evidence to this point for any organic molecules on Io and little hint of carbon of any kind. But it’s also worth keeping in mind that any organic molecules would be extremely difficult to find in Io’s atmosphere — they wouldn’t last long given the radiation environment at the surface. Energy, of course, is plentiful, and the author studies the possibility of chemical and magnetic energy’s role in astrobiology.

I’m not putting my money on Io as a home for life, and even Schulze-Makuch notes that the possibility has to be considered a long-shot. When we have exploratory robotic systems in Jupiter space again, Europa is obviously a much more likely candidate, and so, for that matter, is Ganymede. But a habitable niche in Io’s subsurface can’t be ruled out, even if radiation levels make shielding a robotic probe of the planet a dicey proposition. Until such a probe becomes possible, though, a clear view of Io with adaptive optics may be our best way to observe it.

The paper is Schulze-Makuch, “Io: Is Life Possible Between Fire and Ice?” Journal of Cosmology Vol. 5 (2010), pp. 912-919 (available online).


Comments on this entry are closed.

  • Scott Galas June 22, 2010, 11:06

    I think the adaptive optics development regarding the Large Binocular Telescope in Arizona is huge. It’s EXTREMELY expensive to put space telescopes (or anything else) into Low Earth Orbit or beyond — the current cost, I believe, is roughly $1,000 – $10,000 per pound (depending on the launch vehicle and orbit desired). If we can ivest that money into ground-based observatories (at least those at optical wavelengths) then we can make major headway into astronomical research. Hopefully this leads us down a path where we can get better and better images of nearby exoplanets without having to wait (and pay) for launches of space-based observatories.

  • Enzo June 22, 2010, 16:47

    This page on the LBT site has a simulation of Io seen with two mirrors :

    Scroll down and click on the image.
    It looks similar to the images of Io obtained by New Horizon.

  • Carl Keller June 22, 2010, 19:03

    Here’s one link to the visit to Io and Jupiter Enzo mentioned:


  • Administrator June 22, 2010, 19:50

    The New Horizon images are terrific, and I wish I had thought to use one in the article. But the Cassini snap was also a splendid thing. This is from the article Carl linked to:

    The mission’s investigations of Jupiter’s four largest moons focused on Io, the closest to Jupiter, which has active volcanoes that blast tons of material into the Jovian magnetosphere and beyond. New Horizons spied 11 different volcanic plumes of varying size, three of which were seen for the first time. One, a spectacular 200-mile-high eruption rising above the volcano Tvashtar, provided a unique opportunity to trace plume structure and motion. New Horizons’ global map of Io’s surface confirms the moon’s status as the solar system’s most active body, showing more than 20 geological changes since the Galileo Jupiter orbiter provided the last close-up look in 2001.

  • bigdan201 June 22, 2010, 23:14

    We definitely can’t be limited in our views of exobiology – considering the wide range of habitats of life here on earth, we have to consider that exobiology will be at least as flexible as extremophiles here.

    This discussion, by the way, reminds me of when I was studying planets in elementary school. I recall other kids saying that Io looked like a pizza.. lol.

    Anyway, these adaptive optics are an amazing breakthrough. Being able to view the stars with clarity from the ground, without having to get to orbit, opens up a wide range of opportunities. We will be able to make many more observations of space and do science even more productively.

    I wonder if these adaptive optics will help in the exoplanet hunt? It seems likely, considering the dramatic difference in the comparison picture of the triple star.

  • James Jason Wentworth June 23, 2010, 6:04

    The advances in adaptive optics technology that allow direct imaging of gas giant exoplanets (and should eventually–perhaps from space telescopes–enable direct imaging and spectroscopy of Earth-size exoplanets) also raise a possibility concerning astronomers, if any, on such worlds.

    If humans can almost do this now, any nearby (within 100 light years or so) technological civilizations that are a few decades to several centuries more advanced than humanity have certainly known about Earth and the fact that there is life here for a long time. While I am *not* saying that Earth was visited in the distant past or is being visited now, one of the main arguments against it–that “we shouldn’t feel so ‘special’ or ‘flattered’ as to expect visitors to our average planet in the rural outskirts of the galaxy”–has been effectively “put to bed.”

    If an interstellar probe or a crewed interstellar expedition from the “stellar neighborhood” were to arrive tomorrow, the probe or the crew would not have just stumbled upon our planetary system when approaching our Sun–the civilization behind either venture would have known about us before the ship(s) embarked upon its/their journey. Also, interstellar probes and starships are probably too expensive even for advanced civilizations to potentially waste trips to stars that either have no planets or no life-bearing (or colonizable) worlds.

  • Darrell E June 23, 2010, 10:37

    That is just fantastic. It is a vary rare thing that a new system exceeds all expectations. Really looking forward to seeing what the LBT is capable of once this new adaptive optics system is installed in both scopes.

    Another, well not quite as exciting but very good, thing has happened recently concerning ground based telescopes. The ESO Council has finished the selection process and chosen the site for their European Extremely Large Telescope (E-ELT), a telescope with a 42 meter diameter primary mirror. The chosen site is Cerro Armazones which is about 20 km away from the ESO’s VLT at Cerro Paranal in Chile’s Atacama Desert. With site selection complete plans can be finalized and the E-ELT is now scheduled to begin construction by the end of 2010 and be operating by 2018.

  • djlactin June 23, 2010, 14:53

    Does anyone want to take wager: By the time the New Horizons probe reaches Pluto, adaptive optics technology will provide better images of Pluto than the probe?

  • Adam June 24, 2010, 6:14

    As NH will get better than 100 metre resolution we can work out the baseline for an interferometer to achieve the same. In visible light, say 0.5 micrometers, the limit of distinguishable detail 100 metres apart needs an aperture of 30,500 metres for Pluto’s distance of ~5 trillion metres. So, no, AO won’t see Pluto better, not unless the scopes are really, really far apart and their optical signal can be combined as a virtual interference pattern to analyze. A challenge, though there’s nothing unphysical in the idea, it’s not happening soon enough.

  • Carl Keller June 24, 2010, 6:15

    Hi, djlactin,

    New Horizons resolution will be just under 50 meters, about football-field size as this NASA site states http://www.nasa.gov/multimedia/podcasting/mission_update_newhorizons.html

    The new telescope technology will not be equal to that. But even though, say, our moon can be studied close-hand from observatories, there’s been many probes sent there, and now they’ve been joined from China, Japan, and India. The utilization of probes… even fast fly-bys… use many more packages than just cameras to study the object. Aboard New Horizons, there are LORRI, Ralph, Alice, REX, PAM, and SDC (which will tell how much dust it encounters well after the Pluto system encounter ). http://sites.google.com/site/newhorizonsphy111/

  • Adam June 24, 2010, 6:33

    BTW the E-ELT’s resolution will show an image of Pluto about 32 pixels wide, if the pixels are packed to the optical limit. That’s pretty good for a planet so far away. Two E-ELTs 200 metres apart would increase that to ~160 pixels or so.

    There’s been some discussion of a Exosolar Planet Mapper able to produce ~100 pixel images of Earth-like planets up to ~10 pc away. At that extreme, some 300 quadrillion metres away, an Earth-like planet with a ~130 km resolution needs a telescope some 1,400 km wide. While it’s tempting to say an interferometer that big is doable since radiotelescopes have been combined in bigger interferometers there’s a major problem. The photons reflected off the planet have spread themselves far and wide across an immense spherical wavefront. At 10 pc 1 square metre of reflecting surface of the planet has had its rays spread over ~2.1E+21 square metres. Each photon now has ~2 square metres to itself. To get a decent signal we’d have to catch a lot of photons with a lot of telescopes and keep extraneous noise out. Tricky.

  • Mike August 9, 2010, 10:33

    The NASA press release at http://www.nasa.gov/mission_pages/hubble/science/pluto-20100204.html says that Hubble’s images of Pluto are “a few pixels wide” and the LBT is supposed to have ten times the resolving power of Hubble. Does this mean that the LBT will have greater resolving power than the E-ELT?

  • ljk September 8, 2010, 1:56

    Release No.: 2010-14

    For Release: Tuesday, September 07, 2010 09:00:00 AM EDT

    Can We Spot Volcanoes on Alien Worlds? Astronomers Say Yes.

    Cambridge, MA – Volcanoes display the awesome power of Nature like few other events. Earlier this year, ash from an Icelandic volcano disrupted air travel throughout much of northern Europe. Yet this recent eruption pales next to the fury of Jupiter’s moon Io, the most volcanic body in our solar system.

    Now that astronomers are finding rocky worlds orbiting distant stars, they’re asking the next logical questions: Do any of those worlds have volcanoes? And if so, could we detect them? Work by theorists at the Harvard-Smithsonian Center for Astrophysics suggests that the answer to the latter is a qualified “Yes.”

    “You would need something truly earthshaking, an eruption that dumped a lot of gases into the atmosphere,” said Smithsonian astronomer Lisa Kaltenegger. “Using the James Webb Space Telescope, we could spot an eruption 10 to 100 times the size of Pinatubo for the closest stars,” she added.

    Astronomers are decades away from being able to image the surface of an alien world, or exoplanet. However, in a few cases they have been able to detect exoplanet atmospheres for gas giants known as “hot Jupiters.” An eruption sends out fumes and various gases, so volcanic activity on a rocky exoplanet might leave a telltale atmospheric signature.

    To examine which volcanic gases might be detectable, Kaltenegger and her Harvard colleagues, Wade Henning and Dimitar Sasselov, developed a model for eruptions on an Earth-like exoplanet based on the present-day Earth. They found that sulfur dioxide from a very large, explosive eruption is potentially measurable because a lot is produced and it is slow to wash out of the air.

    Full article here:


  • ljk September 16, 2010, 12:51

    This blog is dedicated to everything about Io:


  • ljk October 5, 2010, 21:20


    Io in True Color

    Credit: Galileo Project, JPL, NASA

    Explanation: The strangest moon in the Solar System is bright yellow. This picture, an attempt to show how Io would appear in the “true colors” perceptible to the average human eye, was taken in 1999 July by the Galileo spacecraft that orbited Jupiter from 1995 to 2003. Io’s colors derive from sulfur and molten silicate rock. The unusual surface of Io is kept very young by its system of active volcanoes. The intense tidal gravity of Jupiter stretches Io and damps wobbles caused by Jupiter’s other Galilean moons. The resulting friction greatly heats Io’s interior, causing molten rock to explode through the surface. Io’s volcanoes are so active that they are effectively turning the whole moon inside out. Some of Io’s volcanic lava is so hot it glows in the dark.

  • ljk December 12, 2010, 14:47
  • ljk October 17, 2012, 12:53

    This makes one realize that Io’s active volcanoes could have been detected well before Pioneer and especially Voyager flew by Jupiter had astronomers thought in that direction:


  • ljk November 13, 2012, 10:08


    Discovery of Volcanic Activity on Io. A Historical Review

    Authors: L. A. Morabito (1) ((1) Victor Valley College, Victorville, CA, USA)
    (Submitted on 12 Nov 2012)

    Abstract: In the 2 March 1979 issue of Science 203 S. J. Peale, P. Cassen and R. T. Reynolds published their paper “Melting of Io by tidal dissipation” indicating “the dissipation of tidal energy in Jupiter’s moon Io is likely to have melted a major fraction of the mass.” The conclusion of their paper was that “consequences of a largely molten interior may be evident in pictures of Io’s surface returned by Voyager 1.” Just three days after that, the Voyager 1 spacecraft would pass within 0.3 Jupiter radii of Io.

    The Jet Propulsion Laboratory navigation team’s orbit estimation program as well as the team members themselves performed flawlessly. In regards to the optical navigation component image extraction of satellite centers in Voyager pictures taken for optical navigation at Jupiter rms post fit residuals were less than 0.25 pixels.

    The cognizant engineer of the Optical Navigation Image Processing System was astronomer Linda Morabito.

    Four days after the Voyager 1 encounter with Jupiter, after preforming image processing on a picture of Io taken by the spacecraft the day before, something anomalous emerged off the limb of Io.

    This historical review written by the discoverer recounts her minute-by-minute quest to identify what was a volcanic plume, the first evidence of active volcanism seen beyond Earth. Many ingredients of the account reflect historic themes in the process of scientific discovery.

    Comments: 30 pages, 12 figures

    Subjects: History and Philosophy of Physics (physics.hist-ph); Earth and Planetary Astrophysics (astro-ph.EP); Popular Physics (physics.pop-ph)

    Cite as: arXiv:1211.2554 [physics.hist-ph]

    (or arXiv:1211.2554v1 [physics.hist-ph] for this version)

    Submission history

    From: Linda Morabito [view email]

    [v1] Mon, 12 Nov 2012 10:38:30 GMT (5039kb)

  • ljk April 5, 2013, 9:29

    4 April 2013

    ** Contacts are listed below. **

    Text, images, and video:



    Jupiter’s moon Io is the most volcanically active world in the solar system, with hundreds of volcanoes, some erupting lava fountains up to 250 miles high. However, concentrations of volcanic activity are significantly displaced from where they are expected to be based on models that predict how the moon’s interior is heated, according to NASA and European Space Agency researchers.

    Io is caught in a tug-of-war between Jupiter’s massive gravity and the smaller but precisely timed pulls from two neighboring moons that orbit further from Jupiter — Europa and Ganymede. Io orbits faster than these other moons, completing two orbits every time Europa finishes one, and four orbits for each one Ganymede makes. This regular timing means that Io feels the strongest gravitational pull from its neighboring moons in the same orbital location, which distorts Io’s orbit into an oval shape. This in turn causes Io to flex as it moves around Jupiter.

    For example, as Io gets closer to Jupiter, the giant planet’s powerful gravity deforms the moon toward it and then, as Io moves farther away, the gravitational pull decreases and the moon relaxes. The flexing from gravity causes tidal heating — in the same way that you can heat up a spot on a wire coat hanger by repeatedly bending it, the flexing creates friction in Io’s interior, which generates the tremendous heat that powers the moon’s extreme volcanism.

    The question remains regarding exactly how this tidal heating affects the moon’s interior. Some propose it heats up the deep interior, but the prevailing view is that most of the heating occurs within a relatively shallow layer under the crust, called the asthenosphere. The asthenosphere is where rock behaves like putty, slowly deforming under heat and pressure.

    “Our analysis supports the prevailing view that most of the heat is generated in the asthenosphere, but we found that volcanic activity is located 30 to 60 degrees East from where we expect it to be,” said Christopher Hamilton of the University of Maryland, College Park. Hamilton, who is stationed at NASA’s Goddard Space Flight Center in Greenbelt, Md., is lead author of a paper about this research published January 1 in Earth and Planetary Science Letters [http://dx.doi.org/10.1016/j.epsl.2012.10.032].

    Hamilton and his team performed the spatial analysis using the a new, global geologic map of Io, produced by David Williams of Arizona State University, Tempe, Ariz., and his colleagues using data from NASA spacecraft. The map provides the most comprehensive inventory of Io’s volcanoes to date, thereby enabling patterns of volcanism to be explored in unprecedented detail. Assuming that the volcanoes are located above where the most internal heating occurs, the team tested a range of interior models by comparing observed locations of volcanic activity to predicted tidal heating patterns.

    “We performed the first rigorous statistical analysis of the distribution of volcanoes in the new global geologic map of Io,” says Hamilton. “We found a systematic eastward offset between observed and predicted volcano locations that can’t be reconciled with any existing solid body tidal heating models.”

    Possibilities to explain the offset include a faster than expected rotation for Io, an interior structure that permits magma to travel significant distances from where the most heating occurs to the points where it is able erupt on the surface, or a missing component in existing tidal heating models, like fluid tides from an underground magma ocean, according to the team.

    The magnetometer instrument on NASA’s Galileo mission detected a magnetic field around Io, suggesting the presence of a global subsurface magma ocean. As Io orbits Jupiter, it moves inside the planet’s vast magnetic field. Researchers think this could induce a magnetic field in Io if it had a global ocean of electrically conducting magma.

    “Our analysis supports a global subsurface magma ocean scenario as one possible explanation for the offset between predicted and observed volcano locations on Io,” says Hamilton. “However, Io’s magma ocean would not be like the oceans on Earth. Instead of being a completely fluid layer, Io’s magma ocean would probably be more like a sponge with at least 20 percent silicate melt within a matrix of slowly deformable rock.”

    Tidal heating is also thought to be responsible for oceans of liquid water likely to exist beneath the icy crusts of Europa and Saturn’s moon Enceladus. Since liquid water is a necessary ingredient for life, some researchers propose that life might exist in these subsurface seas if a useable energy source and a supply of raw materials are present as well. These worlds are far too cold to support liquid water on their surfaces, so a better understanding of how tidal heating works may reveal how it could sustain life in otherwise inhospitable places throughout the universe.

    “The unexpected eastward offset of the volcano locations is a clue that something is missing in our understanding of Io,” says Hamilton. “In a way, that’s our most important result. Our understanding of tidal heat production and its relationship to surface volcanism is incomplete. The interpretation for why we have the offset and other statistical patterns we observed is open, but I think we’ve enabled a lot of new questions, which is good.”

    Io’s volcanism is so extensive that it gets completely resurfaced about once every million years or so, actually quite fast compared to the 4.5-billion-year age of the solar system. So in order to know more about Io’s past, we have to understand its interior structure better, because its surface is too young to record its full history, according to Hamilton.


    Nancy Neal-Jones / Bill Steigerwald
    NASA’s Goddard Space Flight Center, Greenbelt, Md.
    +1 301-286-0039 / -5017
    nancy.n.jones@nasa.gov / william.a.steigerwald@nasa.gov

    The research was funded by NASA, the NASA Postdoctoral Program, administered by Oak Ridge Associated Universities, and the European Space Agency.