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Volcanowatch

November 4, 2004

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


Kilauea provides a basis for research into alien atmospheres

Thomas Jaggar, the first director of the Hawaiian Volcano Observatory, from 1912-1940, probably never imagined that the gas compositions he measured in 1918-19 at the summit of Kilauea Volcano would have such far-reaching applications in the future. He could never have suspected that his data would be incorporated into investigations into volcanic gases on other planets and the hunt for extraterrestrial life!

Researchers investigating the volcanic gases in the atmosphere of Venus and Mars use the gas compositions measured by Jaggar from a summit lava lake at Kilauea in order to calculate possible volcanic gas compositions. This information is then compared to data from telescopes and from spectroscopy performed during flybys and landing probes.

The planet Venus has more volcanoes than any other planet in our solar system. The surface is liberally dotted with them. The volcanoes on Venus are mostly shield volcanoes-like those of the Hawaiian Islands-probably related to subsurface hotspots and areas of weakened crust. Mauna Loa is around 120 km across at its base and rises 8 km from the seafloor, whereas a large shield volcano on Venus is 700 km across and 5.5 km high. So the Venusian shields are broader, but flatter.

The probes that were sent to Venus showed us a truly inhospitable planet. The atmospheric pressure on Venus at the surface is nearly 97 times the atmospheric pressure on Earth at sea level, and Venus is extremely hot, around 480 degrees Celsius. The high pressure prevents some gases from escaping from the magma, which means that explosive volcanic activity is rare on Venus. The volcanic gas compositions are expected to be dominated by the less soluble gases from the magma such as carbon dioxide.

The volcanic gas calculations use Jaggar's data with the hydrogen and carbon content adjusted for the case of Venus. They show that the volcanic gas compositions of Venus could be significantly different from those found here. Halogenated (chlorine and fluorine) sulfur compounds that might be degassing from the Venusian volcanoes in large quantities are rare on Earth. If the volcanoes of Venus are still active, we should expect to find these bizarre compounds in the atmosphere.

Studies of the atmosphere of Venus, however, have shown that something very strange is going on. Two gases, hydrogen sulfide and sulfur dioxide (both of which degas from terrestrial volcanoes), are present in the atmosphere of Venus. These two gases, which react with each other, are not seen in the same place unless something is producing them. It follows, therefore, that something is continuously producing each of these gases. Their abundance does not agree with the models of volcanic gas compositions predicted using Jaggar's data. On Earth, these gases can be produced by anaerobic bacteria.

How could bacteria possibly survive under such harsh conditions? Researchers have found that at an altitude of 50 km (around 30 miles), the atmospheric pressure on Venus is similar to that on Earth at sea level, and temperatures reach a balmy 50 to 70 degrees Celsius. Airborne bacteria might be able to survive in the upper clouds of Venus.

Mars, in contrast, has a very low atmospheric pressure, and it appears that volcanic gas compositions would be similar to those produced on Earth-in more ways than we first thought. In April 2004, researchers found trace amounts of methane in Mars' atmosphere. On Earth, methane is mainly produced by microbes, but it is also produced volcanically. Are there outgassing hotspots on Mars today? Is there-or was there-life on Mars? This discovery has boosted hopes of answering these questions once and for all.

Activity update

Eruptive activity at Pu`u `O`o continues. Surface flows fed from the PKK tube have descended Pulama pali in two widely spaced lobes, about 1 km (0.6 mi) apart. The west arm reached the coastal plain early on November 2. As of late afternoon on November 3, it was about 1 km (0.6 mi) from the coast, which, if it stays the course, it will intersect near Lae`apuki. The terminus of the east arm is advancing much more slowly and is currently at the 520-ft elevation. New flows near the top of the pali are overriding this arm. Break outs also continue along the PKK flow above the pali to about the 2250-foot elevation. The eruptive activity in the crater of Pu`u `O`o remains weak, with several spatter cones glowing but not doing much else.

Two earthquakes were reported felt on the island during the week ending early on November 4. A magnitude 2.8 earthquake at 6:23 a.m. on October 29 was located 7 km (4 miles) west of Kilauea Volcano's summit. The event occurred at a depth of 6 km (3.7 miles). The second felt earthquake on November 4 at 3:25 a.m. was located beneath Kohala Volcano 10 km (6 miles) northeast of Waimea. The magnitude 2.2 event had a depth of 26 km (16 miles).

Mauna Loa is not erupting. The summit region continues to inflate slowly. HVO located 39 small earthquakes recorded deep beneath the summit area, down from 159 the week before. Nearly all of the earthquakes of this ongoing activity are of long-period type and deep, 40 km (23 miles) or more.

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Updated: November 9, 2004 (pnf)