Mercury’s Surface is Full of Sulfur

The southern portion of Mercury’s Vivaldi basin and outlying rugged terrain

Named for the 17th-century Venetian composer, the southern half of Mercury’s Vivaldi basin is seen in this image acquired on August 26 by NASA’s MESSENGER spacecraft. The 213-km (132-mile) -wide crater’s smooth floor is contrasted by the incredibly rugged terrain beyond its outermost ring — a result of the ejected material that was flung out from the impact site and emphasized by the low angle of illumination.

The floor of the crater remained relatively smooth due to molten material that erupted in the wake of the impact event, flooding the basin.

Recent findings from the MESSENGER mission have revealed variations in Mercury’s surface composition due to volcanism that occurred at different times, as well as a surprising concentration of elements like magnesium and sulfur — much more so than any of the other terrestrial planets.

In results to be published in the Journal of Geophysical Research, scientists report that Mercury’s volcanic smooth plains differ in composition from older surrounding terrains. The older terrain has higher ratios of magnesium to silicon, sulfur to silicon, and calcium to silicon, but lower ratios of aluminum to silicon, suggesting that the smooth plains material erupted from a magma source that was chemically different from the source of the material in the older regions, according to Shoshana Weider of the Carnegie Institution of Washington, the lead author on the paper.

Mercury’s surface was also found to be high in magnesium and sulfur-enriched minerals.

“None of the other terrestrial planets have such high levels of sulfur. We are seeing about ten times the amount of sulfur than on Earth and Mars,” Weider said. “In terms of magnesium, we do have some materials on Earth that are high in magnesium. They tend to be ancient volcanic rocks that formed from very hot lavas. So this composition on Mercury tells us that eruptions of high-temperature lavas might have formed these high-magnesium materials.”

Read: MESSENGER Reveals Mercury’s Colors

The data was gathered with MESSENGER’s X-Ray Spectrometer (XRS) — one of two instruments designed to measure the abundances of many key elements in the top 2mm of Mercury’s crust. XRS detects emissions from elements in the 1-10 kiloelectron-volt (keV) range – specifically, magnesium, aluminum, silicon, sulfur, calcium, titanium, and iron.

Read more on the MESSENGER mission site here.

Inset image: A global mosaic of Mercury from MESSENGER (2011). Image credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Is Earth Alive? Scientists Seek Sulfur For An Answer

[/caption]

Researchers at the University of Maryland have discovered a way to identify and track sulfuric compounds in Earth’s marine environment, opening a path to either refute or support a decades-old hypothesis that our planet can be compared to a singular, self-regulating, living organism — a.k.a. the Gaia theory.

Proposed by scientists James Lovelock and Lynn Margulis in the 70s, the Gaia theory likens Earth to a self-supporting singular life form, similar to a cell. The theory claims that, rather than being merely a stage upon which life exists, life — in all forms — works to actively construct an Earthly environment in which it can thrive.

Although named after the Greek goddess of Earth, the Gaia theory is not so much about mythology or New Age mysticism as it is about biology, chemistry and geology — and how they all interact to make our world suitable for living things.

Once called the Gaia hypothesis, enough scientific cross-disciplinary support has since been discovered that it’s now commonly referred to as a theory.

Marine phytoplankton -- like these diatoms -- may produce sulfur compounds that can be transmitted into the air, affecting climate. (NOAA image)

One facet of the Gaia theory is that sulfur compounds would be created by microscopic marine organisms — such as phytoplankton and algae — and these compounds could be transmitted into the air, and eventually (in some form) to the land, thus helping to support a sulfur cycle.

Sulfur is a key element in both organic and inorganic compounds. The tenth most abundant element in the Universe, sulfur is crucial to climate regulation — as well as life as we know it.

In particular, two sulfur compounds — dimethylsulfoniopropionate and its atmospherically-oxidized version, dimethylsulfide — are considered to be likely candidates for the products created by marine life. It’s these two compounds that UMD researcher Harry Oduro, along with geochemist and professor James Farquhar and marine biologist Kathryn Van Alstyne (of Western Washington University) have discovered a way to track across multiple environments, from sea to air to land, allowing scientists to trace which isotopes are coming from what sources.

“What Harry did in this research was to devise a way to isolate and measure the sulfur isotopic composition of these two sulfur compounds,” said Farquhar. “This was a very difficult measurement to do right, and his measurements revealed an unexpected variability in an isotopic signal that appears to be related to the way the sulfur is metabolized.”

The team’s research can be used to measure how the organisms are producing the compounds, under which circumstances and how they are ultimately affecting their — and our — environment in the process.

“The ability to do this could help us answer important climate questions, and ultimately better predict climate changes,” said Farquhar. “And it may even help us to better trace connections between dimethylsulfide emissions and sulfate aerosols, ultimately testing a coupling in the Gaia hypothesis.”

Whether or not Earth can be called a singular — or possibly even sentient — living organism of which all organisms are contributing members thereof may still be up for debate, but it is fairly well-accepted that life can shape and alter its own environment (and in the case of humans, often for the worse.) Research like this can help science determine just how far-reaching those alterations may be.

The study appears in this week’s Online Early Edition of the Proceedings of the National Academy of Sciences (PNAS).

Read more on the University of Maryland’s news page here.

Image credit: ESA ©2009 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA. Edited by J. Major.