New molecules detected in Io's atmosphere

Sep 19, 2013 by Shannon Hall, Universe Today
An image of Io taken by the automated spacecraft: Galileo. Credit: NASA

Io – Jupiter's innermost Galilean moon – is the most geologically active body in the Solar System. With over 400 active volcanic regions, plumes of sulfur can climb as high as 300 miles above the surface. It is dotted with more than 100 mountains, some of which are taller than Mount Everest. In between the volcanoes and mountains there are extensive lava flows and floodplains of liquid rock.

Intense volcanic activity leads to a thin atmosphere consisting mainly of (SO2), with minor species including sulfur monoxide (SO), (NaCl), and atomic sulfur and oxygen. Despite Io's close proximity to the Earth the composition of its atmosphere remains poorly constrained. Models predict a variety of other molecules that should be present but have not been observed yet.

Recently a team of astronomers from institutions across the United States, France, and Sweden, set out to better constrain Io's atmosphere. They detected the second-most abundant isotope of sulfur (34-S) and tentatively detected (KCl). The latter is produced in – suggesting that these plumes continuously contribute to Io's atmosphere.

Expected yet undetected molecular species include potassium chloride (KCl), silicone monoxide (SiO), disulfur monoxide (S2O), and various isotopes of sulfur. Most of these elements emit in .

"Depending on their geometry, some molecules emit at well known frequencies when they change rotational state," Dr. Arielle Moullet, lead author on the study, told Universe Today. "These spectral features are called rotational lines and show up in the (sub)millimeter spectral range."

The Atacama Pathfinder (APEX) antenna. Credit: ESO

These observations were therefore obtained at the Atacama Pathfinder Experiment (APEX) antenna – a radio telescope located 16,700 feet above sea level in northern Chile. The main dish has a diameter of 12 meters, and is a prototype antenna for the Atacama Large Millimeter Array (ALMA).

Following 16.5 hours of total observation time and months of data reduction and analysis, Moullet et al. made a tentative detection of potassium chloride (KCl). Io's volcanic ejecta produce a large plasma torus around Jupiter, which inlcudes many molecular species including potassium. This detection is therefore considered the "missing link" between Io and this plasma torus.

The team also made the first detection of one of Sulfur's isotopes known as 34-S. Sulfur has 25 known isotopes – variants of sulfur that still have 16 protons but differ in their number of neutrons. 34-S is the second most abundant isotope with 18 neutrons.

Previously, the first-most abundant isotope of , 32-S with 16 neutrons, had been detected. Surprisingly the ratio between the two (34/32 S) is twice as high as the solar system reference, suggesting that there is an abundance of 34-S. A fraction this high has only been reported before in a distant quasar – an early galaxy consisting of an intensely luminous core powered by a huge black hole.

"This result tells us that there probably is some fractionation process that we haven't yet identified, which is happening either in the magma, at the surface, or in the atmosphere itself," explains Dr. Moullet. Something somewhere is producing an unexplained abundance of this isotope.

Other expected yet undetected molecules including silicone monoxide and disulfur monoxide remain undetected. It is possible that these molecules are simply not present, but more likely that the observations are not sensitive enough to detect them.

"To perform a deeper spectral search with a better sensitivity, our group has been awarded observation time with the Atacama Large Millimeter Array, a cutting edge interferometric facility in Chile, which will eventually include more than fifty 12-meter wide dishes," explains Dr. Moullet. "We are in the process of analyzing our first dataset obtained with sixteen antennas, which is already much more sensitive than the APEX data."

While Io is certainly an extreme example, it will likely help us characterize volcanism in general – providing a better understanding of volcanism here on Earth as well as outside the Solar System.

The paper has been accepted for publication in The Astrophysical Journal and is available for download here.

Explore further: Video gives astronaut's-eye view inside NASA's Orion spacecraft

add to favorites email to friend print save as pdf

Related Stories

The Atmosphere of Io

Jun 14, 2010

(PhysOrg.com) -- Io is one of the four moons of Jupiter that Galileo discovered after he turned his new telescope heavenward. They shocked him and his contemporaries because they demonstrated that heavenly ...

Major volcanic eruption seen on Jupiter's moon Io

Aug 26, 2013

Recent observations of Jupiter's moon Io has revealed a massive volcanic eruption taking place 628,300,000 km (390,400,000 miles) from Earth. Io, the innermost of the four largest moons around Jupiter, is ...

New views of the cosmos

Nov 02, 2011

Though it won’t be completed until 2013, the Atacama Large Millimeter/submillimeter Array (ALMA), a radio telescope observatory under construction in northern Chile, is already the most powerful and complex ...

Ancient Earth crust stored in deep mantle

Apr 24, 2013

Scientists have long believed that lava erupted from certain oceanic volcanoes contains materials from the early Earth's crust. But decisive evidence for this phenomenon has proven elusive. New research from ...

Recommended for you

SDO captures images of two mid-level flares

Dec 19, 2014

The sun emitted a mid-level flare on Dec. 18, 2014, at 4:58 p.m. EST. NASA's Solar Dynamics Observatory, which watches the sun constantly, captured an image of the event. Solar flares are powerful bursts ...

Why is Venus so horrible?

Dec 19, 2014

Venus sucks. Seriously, it's the worst. The global temperature is as hot as an oven, the atmospheric pressure is 90 times Earth, and it rains sulfuric acid. Every part of the surface of Venus would kill you ...

Image: Christmas wrapping the Sentinel-3A antenna

Dec 19, 2014

The moment a team of technicians, gowned like hospital surgeons, wraps the Sentinel-3A radar altimeter in multilayer insulation to protect it from the temperature extremes found in Earth orbit.

Video: Flying over Becquerel

Dec 19, 2014

This latest release from the camera on ESA's Mars Express is a simulated flight over the Becquerel crater, showing large-scale deposits of sedimentary material.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.