Exploration of volcanoes within our solar system has been much like the exploration of Hawaiian volcanoes in the 19th century: sporadic. We now know where most of the volcanoes beyond Earth are, but know little about how they work. But bits of information are being collected, and whether they are from Earth-based observations, satellite imagery, or fly-by missions, every piece is important, because our best understanding will come from compiling all available data from every source.
Even though exploration of planetary volcanoes has been sporadic, exciting discoveries have been made. And some of these discoveries have revealed volcanic features similar to those found on Hawaiian volcanoes.
Active volcanism on Io, one of Jupiter’s moons, was first discovered by the Voyager 1 spacecraft during a fly-by mission in March 1979. Since then, more information has been obtained from limited observations by four additional NASA spacecraft as they passed through the solar system and from more frequent observations from the Hubble Space Telescope. A complete map of Io’s volcanoes was published by the U.S. Geological Survey in 2011 (pubs.usgs.gov/sim/3168).
Combining these data, planetary volcanologists have hypothesized that Loki Patera, the largest depression on Io, hosts an active lava lake. The temperatures of this lava lake are in the right range for a molten silicate, but scientists can’t differentiate exactly what type of lava is in the lake by temperature alone.
Loki Patera and the lava lake it contains are huge by Earth standards — about 125 miles in diameter, which is larger than the entire Big Island. Detailed analyses of all the data show that the lava lake is probably horseshoe-shaped.
During the 1990s, the Loki Patera lava lake displayed periodic bursts of thermal energy every 18 months, suggesting that the lake was resurfaced by a new solidified crust during each burst. The areas of highest temperature within the lake seem to move during these cycles, so the speed of lake resurfacing appears to be about 1 inch per second. These bursts have been irregular in the past decade.
In the past few years, Earth-based Extremely Large Telescopes (ELTs) have been designed to achieve enough spatial resolution to obtain details of volcanic features on Io, as well as a more continuous record of volcanic activity. The first Earth-based ELT is the Large Binocular Telescope located at an elevation of 10,500 feet on Emerald Peak in the Pinaleno Mountains of Arizona. It consists of two identical 27.6-foot telescopes mounted side-by-side for a combined collecting area of a single 38.7-foot telescope.
Using an infrared camera with this telescope, scientists were able to achieve a final spatial resolution of less than 12 miles on the surface of Io during a one-hour observation on Dec. 24, 2013. At the time, Loki Patera had just finished one of its brightening bursts. The 2013 infrared image also showed two hotspots. These two locations are interpreted to be a persistent hotspot in the southwest portion of the lake (seen before) and another hotspot to the east, which might be the leading edge of the recent lake-resurfacing burst.
Back on Earth, the Kilauea summit lava lake within Halemaumau Crater is 1,000 times smaller than Io’s Loki Patera lava lake, and contains molten basalt. The Halemaumau lava lake continuously circulates, with new crust generated at one side of the lake, then moving across the lake surface at speeds of around 6 inches per second before being consumed at the opposite side. It rarely resurfaces in the way envisioned for the Loki Patera lava lake, but, when it does, the Halemaumau lake resurfaces at about 3 inches per second.
More sophisticated analyses of existing Io data, as well as more imagery data from spacecraft and Earth-based ELTs, will yield additional details of the Loki Patera lava lake. Studies on the behavior of the Halemaumau lava lake are also underway. As scientific papers are published, perhaps comparisons between Earth’s and Io’s lava lakes can be made and will reveal more about planetary volcanoes in the far reaches of our solar system.
Kilauea activity update
Kilauea’s summit lava lake level fluctuated over the past week, but remained well below the Overlook crater (vent) rim and out of direct view from Jaggar Museum. Deflation resulted in the lake reaching a low level on May 26, at about 210 feet below the Overlook crater rim. With subsequent inflation, the lake had reached about 160 feet below the vent rim on May 28.
Kilauea’s East Rift Zone lava flow continues to feed widespread breakouts northeast of Puu Oo. The active flows have been within 5.3 miles of Puu Oo over the past week.
Two earthquakes were reported felt on the Island of Hawaii in the past week. On May 22 at 7:07 p.m., a magnitude-2.9 earthquake occurred 1.3 miles northeast of Waimea at a depth of 10.1 miles. On Thursday, at 5:56 a.m., a magnitude-2.7 earthquake occurred 4.1 miles northwest of Captain Cook at a depth of 8.4 miles.
Visit hvo.wr.usgs.gov for past Volcano Watch articles, Kilauea daily eruption updates and other reports, photos, recent earthquakes, and more; call 967-8862 for a Kilauea summary update; email questions to askHVO@usgs.gov.
‘Volcano Watch is a weekly article and activity update written by scientists at the USGS’s Hawaiian Volcano Observatory.