Better understanding of Earth’s atmospheric chemistry from studying Mars?

Science & Exploration


Long-term research of ozone and water vapour within the environment of Mars may result in higher understanding of atmospheric chemistry for the Earth. A brand new evaluation of information from ESA’s Mars Express mission has revealed that our data of the way in which these atmospheric gases work together with one another is incomplete.

Using 4 martian years of observations from the SPICAM (Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars) instrument, which corresponds to seven and a half Earth years, a crew of researchers from Europe and Russia uncovered the hole in our data when making an attempt to breed their information with a worldwide local weather mannequin of Mars.

Understanding ozone on Mars
Ozone and water vapour don’t make good atmospheric companions. The ozone (O3) is produced when molecules of carbon dioxide (CO2), which includes 95% of the martian environment, are cut up aside by ultraviolet radiation from the Sun. In flip, the ozone might be cut up aside by molecules known as hydrogen radicals (HOX), which include an atom of hydrogen and a number of atoms of oxygen. The hydrogen radicals themselves are produced when water vapour is cut up aside by ultraviolet mild.On Mars, because the carbon dioxide is ubiquitous, there must be a worldwide signature of ozone – until a selected area comprises water vapour. In that circumstance, the water will likely be cut up into hydrogen radicals, which is able to react with the ozone molecule and pull it aside.Thus, wherever SPICAM detected water vapour, it ought to have seen a lower in ozone. The extra water vapour, the much less ozone. The crew investigated this inverse relationship, often known as an anticorrelation. They discovered that they might reproduce the overall inverse nature of it with a local weather mannequin however not obtain the exact relationship. Instead, for a given quantity of water vapour, the mannequin produced solely 50% of the ozone seen within the SPICAM information.

“It suggests that the efficiency of ozone destruction is overstated in the computer simulations,” says Franck Lefèvre, of the Laboratoire atmosphères, milieux, observations spatiales (LATMOS), CNRS/Sorbonne Université, France, who led the examine.At current, nevertheless, the explanation for this over-estimation is just not clear. Understanding the behaviour of hydrogen radicals on Mars is crucial. “It plays a key role in the atmospheric chemistry of Mars but also in the global composition of the planet,” says Franck.The chemical mannequin used on this work was constructed particularly by Franck and colleagues to analyse Mars. It was primarily based on a mannequin of half of the Earth’s higher environment; the mesosphere. Here, between roughly 40-80 kilometres in altitude, the chemistry and situations are broadly much like these present in Mars’s environment.

Ten stuff you didn’t find out about Mars: 5. Ozone
Indeed, the discrepancy discovered within the fashions may have necessary repercussions for the way in which we simulate the Earth’s local weather utilizing atmospheric fashions. This is as a result of the mesosphere on Earth comprises half of the ozone layer, which is able to expertise the identical interactions with HOX as happen on Mars.“HOX chemistry is important for the global equilibrium of the Earth’s ozone layer,” says Franck.So, understanding what is going on within the environment of Mars may benefit the precision with which we are able to carry out local weather simulations on Earth. And with a lot information now out there from SPICAM, the modelling has clearly proven that there’s something we don’t perceive.Could that one thing be the motion of clouds?When Franck and colleagues launched calculations for the way in which HOX is absorbed by the icy particles that make up clouds on Mars, they discovered that extra ozone survived of their fashions. This is as a result of HOX molecules had been absorbed earlier than they might pull aside the ozone. But this solely partially defined their outcomes.“It doesn’t work in all the cases,” says Franck. And so the crew are wanting elsewhere too.One specific space for additional examine is measuring response charges on the low temperatures discovered within the martian environment and Earth’s mesosphere. At current, these are usually not well-known, and so may be skewing the fashions.

Now that the present work has highlighted in a quantitative method the place the gaps lie in our data, the crew will gather extra information utilizing different UV devices working at Mars and proceed their investigations and replace the mannequin.“With Mars Express, we have a completed the longest survey of the martian atmosphere to date, regardless of the mission. We started in 2004, and now have 17 years of data, which has led us to look at almost seven martian years in a row, including four martian years of combined ozone and water vapour measurements before the UV channel of SPICAM, which measured ozone, ceased operating near the end of 2014. This is unique in the story of planetary exploration,” provides Franck Montmessin, additionally from LATMOS, and the principal investigator of the SPICAM instrument.Building on the extraordinary dataset from Mars Express, new outcomes are actually coming in from ESA’s Trace Gas Orbiter, which has been circling Mars since October 2016. It carries two devices, ACS (Atmospheric Chemistry Suite) and NOMAD (Nadir and Occultation for MArs Discovery) which might be analysing the martian environment. NASA’s Maven mission additionally carries ultraviolet gear that displays ozone abundance. So, the very important piece of data that lastly unlocks this thriller may come at any time.The long-term monitoring of atmospheric parameters and their variations by Mars Express gives a singular information set with which to review the martian environment as a fancy dynamic system.“Maybe adding up all these years together will eventually hold the key to how the HOX really controls the martian atmosphere, benefiting our understanding of planetary atmospheres in general,” says Franck Montmessin.

Notes for editors:Relationship between the ozone and water vapor columns on Mars as noticed by SPICAM and calculated by a worldwide local weather mannequin, by F. Lefèvre, et al. (2021) is printed in Journal of Geophysical Research: Planets 126, e2021JE006838.
For extra data, please contact:ESA Media

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