Monitoring Io volcanic Activity

Franck Marchis

Conor Laver, Imke de Pater (UC-Berkeley)

Collaborators: A. Davies, E. Hom, R. Lopes.

Outline

• 2001-2002 monitoring (not again! - published Marchis et al. 2005)

• 2003-2004 Monitoring

• What happened in 2005?

• First OSIRIS data

• Future AO for Keck and beyond

Io in Near infraredIo in Near infrared

• In JHK (1-2.5 m) surface features mainly seen (reflecting Sunlight)

• In LM (3-5 m) thermal output from eruptions

• Brightness of hot spots in multiple bands T and SA of active regions.

J H K L Mz

2003-2004 MonitoringThe Keck Adaptive Optics instrument which provides high angular

resolution images is a perfect tool to monitor the volcanic activity of Io.

Data:Data: Observations were recorded in imaging mode using the NIRC-2 infrared camera mounted on the Keck-10m AO system through several filters spanning 1-5 m on January 26, 2003, March 8, 2003, and May 27-30, 2004.

• At < 2.5 m in J (1. 2 m), H (1.6 m), K (2.2 m) bands, albedo surface features (paterae, pyroclastic deposit fields) are visible with a spatial resolution ~150 km

• At > 3 m, Lp (3.7 m) & Ms (4.8 m) bands, the thermal signatures of active volcanoes (T~500 K) dominate the image.

Analysis:Analysis: After enhancing the image sharpness with AIDA (Hom et al., 2005) or MISTRAL (Mugnier et al., 2004) algorithms, the position and brightness of individual hot spots were determined.

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Jan. 26 2003Observations9 active centers were

seen on one hemisphere (CML=73o). Several of them (A,B,D,E,F,G,H) were active during the Keck Dec. 2001 survey (Marchis et al., 2004) and the Galileo orbits (Lopes et al. 2004)Janus: I=11+/-1 GW/sr/u

marginal in K band

March 08 2003Among 6 active centers detected on this hemisphere

(CML= 145o), 5 (A,B,C,D,E,F) were seen active in the last 3 years.

SSI/Galileo reconstructed image

May 2004• Four nights of Observations (May 27-30)

May 2004• 18 hot spots were detected on the ~70% of the entire

satellite surface. 12 of them are considered as persistent (Lopes-Gautier, 1997 and Marchis et al. 2004). Their temperature and surface are estimated by a one-T black body fit (Taver~500 K). Loki (Q), the most active Ionian volcano, exhibits a low activity in contrast to previous long-term studies (Rathbun et. al.,2003, Howell et al., 2001).

360 180

May 2004

Label Date of Obs.

Coordinates Intensity

In L

(GW/sr/m)

Intensity

In M

(GW/sr/m)

Candidate1 Best T

(K)

Surface

Area

(km2)

D May 27 83.9W,2.3N 1.6±0.3 2.9±0.9 Hi’iaka 445 55 ±1

E May 27 95.4W,16.0N 0.7±0.3 1.9±0.4 Gish Bar 300 1300 ±250

F May 27 118.5W,22.3N 2.2±0.5 4.2±0.7 Amirani 485 41 ±3

G May 27 132.3W,33.8S 0.6±0.1 1.2±0.2 Malik 435 25 ±1

H May 27 144.3W,17.4S 1.2±0.4 1.5±0.1 Tupan 590 5 ±1

I May 27 158.0W,0.6S 1.9±0.3 4.1±0.9 Prometheus 410 139 ±1

A May 28 6.3W,17.5S 59 ±2 64±16 Ilmarinera* >860 37X ±4X

P May 28 309.7,37.1N 3.4±0.7 14.7±1.1 Amaterasu 310 5287±500

Q May 28 311.6W,14.0N 11.4±0.8 40±4 Loki 315 13283±16

R May 28 344.3W,51.7S 9.4±0.7 25±1 Creidne 380 1501 ±100

* Or Angpetu

Intensities are preliminaryContact me, please!

Hot spot ‘0405A’Detected May 28 & May 30, 2004

6.3 W, 17.5SBrightness in Lp: 59.3 +/- 2.1 GW/sr/micron & 52.8 +/- 1.8 GW/sr/micronBrightness in Ms: 63.5 +/- 16 GW/sr/micron & 67.3 +/- 14.1 GW/sr/micronBrightness in Kc: 1.8 +/- 0.1 GW/sr/micron Brightness in H: 0.8 +/- 0.1 GW/sr/micron

Rate of aerial coverage = 1561 m2/s

Total area = 921 km2

Age of surface = 163 hours ~ 6 daysT = 1475 to 300K

Total Output: = 2.4 x 1012 W = 2.5% Io total thermal output

From the shapes of the model fits to the data, certain conclusions can be drawn about the manner of these eruptions. The volcanic activity at Tupan and Janus comes from emitting surfaces covering 44 and 37 km2 respectively, smaller in area than the longer-lived eruption 0405A, which may be either Angpetu or Ilmarina Patera. This eruption covers a much larger area (over 900 km2) and is a more vigorous eruption with a large rate of surface coverage.

What happened in 2005?• Most of our Keck nights were lost due to bad

weather. One snapshot of Io in July 15 revealed a bright hot spot (close to Svarog)

• Alarm program initiated in 2004. ToO time granted on VLT/NACO on two years.

-> no detection unfortunately

~25 observations at Lick -> no outburst

OSIRIS instrument

• Integral Field spectrograph designed to work with Keck OA

• Commissioned in 2005B, offered in 2006A

• R~3400 with an angular resolution of 0.1” in z, J H K band

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OSIRIS

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Io seen through OSIRIS• Proposal submitted for 2006A (PI: I. de

Pater)

• C. Laver, graduate student Thesis project

• April 2006 -> snapshot of Io

• June 2006 -> 2 x half nights dedicated to Io (both hemispheres)

• Results presented here are very preliminary!

April 2006 Run

• Mode used Kbb (1.965 m -2.381 m) • 0.05” scale -> FOV= 0.56” x 2.24”• Mosaic composed of 2 images• 20060417 at 09:13 UT

– Center on Sigurd patera (CML=258o in planetocentric)

– CML= 360-258 = 102o in planetographic referential

April 2006 Runaveraged imageSumming up spectra

2 hot spots detected:- 20060417A - 2% Io total brightness (Dazhbog Regio)- 20060417B - faint - close to Hi’iaka

A

B

Processed by C. Laver

April 2006 Runaveraged imageSumming up spectra

Albedo feature -> Bosphorus Regio

April 2006 RunSO2 lines at 1.982 m and 2.125 m(Schmitt et al., 1994)

detected on the spectraPreliminary work by C. Laver

C. Laver

June 2006 Run• Observations in Hbb (1.473-1.803 m), Kbb (1.965-2.381) • FOV: 0.32” x 1.28” (0.01” / pixel)• Global mosaic made of 6 images ~40 min/spectra• 2 half-nights

– 20060601

– 20060602 centered ~SEP longitude of ~100 degrees

72 images through KbbNo tellurical correction yets~40 min to scan

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Animation by C. Laver

June 2006 Run• 20060601 CML~108o

– Pele (caldera, ring), Loki, Svarog– No bright hot spot

Averaged H band Averaged K bandMosaic by C. Laver

June 2006 runObservations in June 02 (CML~100o)• 20060417A is still active & detectable!• 20060417B is not…

20060417Aawakening of Tvashtar

Most likely candidate: Tvashtar (60N+/-3, 120.3+/-5.5W)Spectra from 0.9-2.5 m recorded (analysis in progress…)

Positions in agreement

• 0914 UT 120.4+/-4 63.6+/- 5

• 0732 UT120.3+/- 5.4 60.0+/-3.3

Will be refined…

Future work• OSIRIS data

– Hot spot spectra– Compositional maps (SO2 and others?)

• NIRC2 observations– Continue to monitor Io when at telescope– Publish our 2003-2005 monitoring result

• Observations in coordination with New Horizon flyby submitted to ESO (VLT/NACO)– Imaging (PI. J. Spencer)– Spectroscopy (PI: K.L. Jessup)

• New Generation of AO at Keck– Make sure that planetary science will be considered

Next generation of AO systems• High quality AO system providing a perfect correction

in JHK (SR>85%) and median in visible (SR>30%)

Spatial resolution45 km

Spatial resolution90 km

Next generation of AO systems• High quality AO system providing a perfect correction

in JHK and median in visible

• First light before 2012!

Next Generation of ground-based telescopes

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TMT - available in 2014 ?

Spatial resolution45 km in NIR10 km in visible