Tag Archives: hydroxyl

Lightning discharges help clean the air of some greenhouse gases

Lightning could have an important ecological function, a duo of new paper reports. According to the findings, such discharges play an important role in clearing gases like methane from the atmosphere.

Image credits Abel Escobar.

As we all know, thunderbolt and lightning, very, very frightening. However, they also seem to be quite fresh. The immense heat and energy released by lightning bolts break apart nitrogen and oxygen molecules in the air, which mix into hydroxyl radicals and hydroperoxyl radical — OH and HO2, respectively. In turn, these highly reactive chemical compounds go on to alter the atmosphere’s chemistry, in particular jump-starting the processes that degrade greenhouse gas compounds such as methane.

Bolt Cleaning

“Through history, people were only interested in lightning bolts because of what they could do on the ground,” says William H. Brune, distinguished professor of meteorology at Penn State and co-author on both of the new papers. “Now there is increasing interest in the weaker electrical discharges in thunderstorms that lead to lightning bolts.”

Data for this research was collected by an instrument plane flown above Colorado and Oklahoma in 2012. The plane followed thunderstorms and lightning discharges in order to understand their effect on the atmosphere.

Initially, the team assumed that the spikes in OH and HO2 signals (atmospheric levels) their devices were picking up must be errors, so they removed them from the dataset to study at a later time. The issue was that the instrument recorded high levels of hydroxyl and hydroperoxyl in stretches of the cloud where there was no visible lightning. A few years ago, Brune actually took the time to analyze it.

Working with a graduate student and research associate, he showed that the spikes could be produced both by sparks and “subvisible discharges” in the lab. After this, they performed a fresh analysis of the thunderstorm and lightning data from 2012.

“With the help of a great undergraduate intern,” said Brune, “we were able to link the huge signals seen by our instrument flying through the thunderstorm clouds to the lightning measurements made from the ground.”

Planes avoid flying through the center of thunderstorms because it’s simply dangerous for them, Brune explains, but they can be used to sample the top portion of the clouds which spread in the direction of the wind — this area of a storm is known as ‘the anvil’. Visible lightning is formed in the part of the anvil near the thunderstorm core.

Most bolts never strike the ground, he adds. This lightning is particularly important for affecting ozone and some greenhouse gas in the upper atmosphere. While we did know that lightning can split water to form hydroxyl and hydroperoxyl, this is the first time it has actually been observed in a live thunderstorm.

The researchers found hydroxyl and hydroperoxyl in areas with subvisible lightning, but very little evidence of ozone and no signs of nitric oxide (which requires visible lightning to form) in these areas. If this type of lightning occurs routinely, its outputs of hydroxyl and hydroperoxyl should be included in atmospheric models (they are not, currently).

Both of these compounds interact with some gases like methane, breaking them down through chemical reactions, and preventing them from realizing their full greenhouse potential.

“Lightning-generated OH (hydroxyl) in all storms happening globally can be responsible for a highly uncertain but substantial 2% to 16% of global atmospheric OH oxidation,” the team explains.

“These results are highly uncertain, partly because we do not know how these measurements apply to the rest of the globe,” said Brune. “We only flew over Colorado and Oklahoma. Most thunderstorms are in the tropics. The whole structure of high plains storms is different than those in the tropics. Clearly, we need more aircraft measurements to reduce this uncertainty.”

The first paper “Extreme oxidant amounts produced by lightning in storm clouds” has been published in the journal Science.

The second paper, “Electrical Discharges Produce Prodigious Amounts of Hydroxyl and Hydroperoxyl Radicals” has been published in the Journal of Geophysical Research: Atmospheres.

Vesta covered in carbon by gentle asteroids

Vesta is “peppered” with carbon materials which researchers believe were left behind by asteroids gently striking its surface.

Vesta is an asteroid itself – but one so large that some astronauts were actually thinking about declaring it a planet, or at least a protoplanet. It is the second largest asteroid in our solar system, second only to Ceres, comprising 9% of the total mass in the asteroid belt. This year, Vesta has been studied in detail by the Dawn spacecraft.

It is actually the first evidence astronomers have about asteroid material across a large body’s surface, and it could explain the curious patterns observed by Dawn, which orbited Vesta from July 2011 to September 2012.

“The earliest images we had of the surface — shortly after going into orbit — were sometimes spectacular examples of very bright and very dark material on the surface,” said researcher Tom McCord of the Bear Fight Institute, a science research facility in Washington state. McCord is the lead author of a study reporting the findings that will be published in the Nov. 1 issue of the journal Nature.

They had three initial theories regarding the dark coloured patterns: they could either be volcanic basalts which are typically black, they could be “shock-melted and darkened” material melted from the surface heat caused by impacts, or it could be carbonic, primitive organic material.

The light spectrum analysis revealead that the black matter came off of asteroids, and that it also contains lots of hydrogen and hydroxyl in the materials, which tends to be present in carbonaceous asteroids.

“All of that is consistent, but it doesn’t [definitively] prove carbonaceous chondrite material,” he said. “There are pieces of material, and there is no evidence of any other source that we can think of, at least.”

Precursor of water found in Moon soil – Sun might be responsible

A group of researchers from the United States found out that the Moon is covered with a soil containing typical water structure. Weirdly enough, the water substructure packed soil is created by a constant stream of charged particles coming from the sun, according to the team.

 

The key is hydroxyl. As you probably know, water typically has 2 Hydrogen atoms and 1 Oxygen atom – H2O; hydroxyl is a precursor of water. Samples returned to Earth by the Apollo missions carry molecules of this precursor, which, according to researchers, developed from a reaction between hydrogen ions in the solar wind.

As Yang Liu at the University of Tennessee explains, the sun was formed 4.5 billion years ago from a cloud of gas; in this reaction, deuterium reacted with hydrogen to form helium. As a result, much unlike other bodies from our solar system, the Sun is deuterium-less. The analyzed hydroxyl samples were also extremely poor in deuterium, which made Liu believe the Sun is the culprit here.

So what does this mean? There is no water in the lunar soil, just a precursor, but this is extremely important, especially for hypothetical future Moon missions.

“Our work shows that the ‘water’ component, the hydroxyl, is widespread in lunar materials, although not in the form of ice or liquid water that can easily be used in a future manned lunar base,” Michigan geological sciences Professor Youxue Zhang said.

So it’s good news, but how the solar hydrogen combined with the oxygen to form hydroxyl is still a matter of scientific debate. However, this doesn’t seem to be a weird or unusual phenomena, so you could probably expect this to take place in other places from our solar system as well – such as Mercury, Vesta, or even Mars.

“A similar mechanism may contribute to hydroxyl on the surfaces of other airless terrestrial bodies where the solar wind directly interacts with the surface,” says the study.

The results were published in Nature Geoscience