Keck AO Observations: Io Volcanism - "Mornes plaines"

By Dr. Franck Marchis
Planetary Astronomer at the Carl Sagan Center for the Study of Life in the Universe, SETI Institute

I'd like to share the first of two blogs on observations of Io that we did using the Keck telescope and its Adaptive Optics (AO) system.

Similar to last year, my summer is busy with the REU (Research Experience for Undergraduates) students of the SETI Institute. I will write a specific post on two students who are working with me and their project in a few days.

I obtained telescope time at the end of June 2010 with the W.M. Keck II telescope and its Adaptive Optics system. Because I could not afford to travel to the Big Island, I decided to conduct these observations from UC-Berkeley, using a dedicated remote control room in the basement of our building. Keaton Burns, one of my REU students, was also there and helped me during these observations. Interestingly, it was his first observation run with an optical telescope. Starting as a newbie with the largest telescope in the world, I am hoping he is not going to get bored too quickly. :-)


Keaton Burn, SETI-REU student in the remote control room at UC-Berkeley,

shortly before the beginning of the observations.

As usual with the W.M. Keck telescope, the night went smoothly even if it was quite intensive. We observed 40 targets (mostly asteroids) with an excellent seeing (~0.7â³) and sky transparency. We are very fortunate to be able to conduct observations from this exceptional site. Mauna Kea is definitely one of the best sites for astronomy. I should also thank our telescope operator (Julie) and our AO support (Hien Tran) for their first class support and their help during this night.

During our night, we took a break of observing asteroids (we are searching for moons around them) and pointed the Keck telescope toward Io. Io, the innermost satellite of Jupiter, is well known for its intensive volcanism. Using AO systems, we use the exquisite angular resolution provided by these instruments mounted on 8-10m class telescopes to monitor its volcanic activity. Our spatial resolution remains limited (~125 km), so we do not see the volcanoes themselves but the thermal output of the fresh magma being erupted.


The above three images of Io were taken at 2.1 um (Kp), 3.8 um (Lp) and 4.7 um (Ms). At longer wavelength range, you can see more active volcanoes (bright dots on the images) since we are sensitive to lower magma temperature.

On the top of monitoring the active volcanoes on Io to determine their temperature and surface area, we were hoping to capture a high temperature volcano (an outburst) like we saw in Feb 2001 for instance. These extremely energetic eruptions are detectable at a shorter wavelength (

The tough reality of being a planetary astronomers: we can't make a major discovery each time we observe... :(

Fore more on this observing run, read my second blog.

July 15, 2010

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