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By Science Hooker, Mar 24 2016 02:16PM

Space scientists often publish research findings based on meteorites that are supposedly from Mars, but how on Earth (forgive the pun) do they know for sure they come from Mars? Why not from another planet? Or from random space debris? Besides, does it really matter where meteorites come from?

What is a meteorite? A meteorite is a relatively small solid piece of rock, often containing metal, that lands on Earth from space. Many form from disintegration of asteroids or comets. Asteroids are rocks greater than 1km3 and comets are icy rocky bodies. However, some meteorites come from planets, such as Mars, and are ejected into space when their surfaces are struck by large impacts. This ejection process is called spallation. When in space the rock is called a meteoroid, and if it happens to impact Earth and survive entry it is then called a meteorite. Scientists have currently confirmed 89 meteorites found on Earth that originate from Mars [1].

How do we know they are from Mars? We have good knowledge of the gas composition in the Martian atmosphere via measurements taken by landers, rovers and satellites. Within meteorites there are tiny pockets of trapped gas, often tightly sealed in melt glass, and by carefully measuring the elemental composition of such gas bubbles using a technique called spectrometry. The spectrometry results can be compared to the known values from Mars. When scientists claim a meteorite is from Mars it is because the gas proportions have matched precisely.

Is this the only test? Although a good initial test, there are other lines of evidence to confirm whether the meteorite came from Mars.

• Rocks from Mars contain iron rich metal oxide minerals such as magnetite, chromite and ilmenite, however, the rocks are poor in pure iron metal [2].

• They all contain the magnetic sulphide mineral called pyrrhotite [3].

• Within certain minerals called olivine and pyroxene there is a chemical element ratio of iron to manganese (Fe:Mn) that is highly distinctive of Mars [2].

• Rocks from Mars possess highly specific oxygen isotope ratios. Isotopes are when the atomic mass of an element, such as oxygen, varies due to the number of neutrons present. Oxygen can be present as O16, O17 or O18. Rocks with the same 18O / 16O ratio usually have the same 17O / 16O ratios. Mars meteorites possess a higher 17O / 16O ratio than rocks from Earth or the moon, and are distinctive from meteorites that have not come from Mars [4].

How can scientists be sure all this information isn’t just contamination from when the meteorite landed on Earth? When meteorites descend incredibly fast through the Earth’s atmosphere a great amount of heat is generated through friction with atmospheric particles. This heat produces a semi-melted outer layer called a fusion crust, which is characteristically dark and shiny. This layer can create an impenetrable barrier to moisture, microbes and other contamination. However, over time even the best seals break and contamination occurs. A great deal of effort is spent assessing whether findings are genuine results or contamination effects [5].

Are all Mars meteorites made of the same stuff? No. Meteorites from Mars divide into three main sub-types and are named after the meteorites that best represent those sub-types. These are called Shergotty, Nakhla and Chassigny, and are collectively known as SNC meteorites. There are a couple of rare Martian meteorites outside of the SNC range, but these will not be discussed here. Shergottites are the most common and are made of basaltic rock, much like the sea floor. There are seven Nakhlites and these are made of clinopyroxenite; these Nakhlites contain the best evidence of ancient water on Mars. Two Chassignites have been found and are made of dunite, a greenish rock caused by the mineral olivine, and in Earth dunites form quite deep in the crust.

Why do these Mars meteorites matter? By studying the chemistry and mineralogy of Mars meteorites we can discover what the conditions of early Mars was like and how these conditions have evolved over time. They help us unpick whether the planet once had vast oceans or were covered in icy glaciers. The ancient environments then inform us as to whether life may have been present, and help us in deciding whether life might currently be present. We are now sure Mars had surface water in its past, and this would have required a thicker atmosphere which has now gone. Some was lost to space, some stored in the poles as CO2 ice. Yet some of the mostly CO2 atmosphere became stored in the crust as the mineral carbonate, which we can study in Mars meteorites. The very same process of capturing atmospheric CO2 in rock is being tried by engineers on Earth to counter dangerous climate change caused by anthropogenic global warming. It is quite possible that the ancient environmental history of early Mars, brought to us in the form of meteorites, can teach us a great deal about managing our own planet’s carbon future.

Also, meteorites are just awesomely cool!

[1] http://www.imca.cc/mars/martian-meteorites-list.htm

[2] http://www.imca.cc/mars/martian-meteorites.htm

[3] Rochette P., Lorand J., Fillion G., Sautter V. (2001). ‘Pyrrhotite and the remanent magnetization of SNC meteorites : a changing perspective on Martian magnetism.’ Earth and Planetary Science Letters 190:1-12.

[4] http://www.psrd.hawaii.edu/Dec01/Oisotopes.html

[5] http://www.astrobio.net/news-exclusive/contamination-impacted-meteorites-can-happen-quickly/

By Science Hooker, Mar 24 2016 01:29PM


The modern surface of Mars displays evidence for past liquid water flows, with mounds and polygons in the Chryse-Acidalia region possibly indicating large bodies of ancient standing liquid (Oehler and Allen, 2012). For liquid water to be stable at the planet’s surface, temperatures of >273.2K and a saturation water vapour pressure of >6.1 mbar are required (Martínez and Renno, 2013). To achieve such conditions, atmospheric pressures >1 bar CO2 have been hypothesised during the late Noachian/early Hesperian period (i.e. ~1.4-3.0 Ga e.g. Fernández-Remolar et al. 2011). Mars' currently thin (6 mbar) atmosphere poses the question of the fate of the hypothesised multi-bar CO2 atmosphere. Estimates for ~270 mbar lost to space (Niles and Michalski, 2011), with ~5 mbar at the poles (Phillips et al. 2011), leaves a minimum 750 mbar unaccounted for.

The nakhlite martian meteorites display clear evidence of low water to rock (W/R) ratio isochemical silicate mineral carbonation (Tomkinson et al. 2013). Such carbonation processes can also be observed in basic to ultra-basic terrestrial rock exposures, such as the Samail peridotite (Oman; Kelemen et al. 2011) and Del Puerto ophiolites (Californian; Blank et al. 2009). The present research project aims to compare martian meteorite petrology and geochemistry with basic to ultra-basic carbonated terrestrial ophiolite analogues, conduct carbonation experiments on terrestrial Mars analogue samples and construct a crust-atmosphere coupling model. By analysing carbon sequestration processes at differing scales and environments, carbonation rates and total silicate carbonation volumes under palaeo-martian atmospheric and mineralogical conditions can be estimated.


Hydration and carbonation of silicate rocks is an important negative feedback process in the terrestrial carbon cycle. Significant atmospheric CO2 removal via silicate weathering partly balances the volcanic CO2 output. Peridotite contains >40% olivine, which can hydrate to form quartz, magnesite and serpentine via reactions 1 to 3 of table 1. These reactions may be followed by carbon sequestration via reactions 4 to 7 of table 1.

Basic to ultra-basic rocks also contain abundant pyroxenes which can hydrate and carbonate via reaction 8 of table 1, usually in two discreet steps through reactions 9 and 10 of table 1. These reactions form highly alkaline travertine springs (pH>11), which have been observed in terrestrial ophiolites worldwide.

Carbonation is exothermic, with the total fully carbonated solid products possessing 44% greater mass than the reactants (Kelemen et al. 2011). This causes cracking (Kelemen and Hirth, 2012), exposing fresh reactant surfaces, although this can be offset by expansion causing reduced porosity (Alt and Teagle, 1999). The raised temperatures increase reaction rates, and a positive feedback mechanism of sustained carbonation can develop.

The crust of Mars is composed of similarly basic to ultra-basic minerals, mostly basalt on the surface (Taylor et al. 2010). By investigating carbonated terrestrial analogues a deeper understanding of Martian crust-atmosphere dynamics can be achieved, possibly resolving currently unexplained martian anomalies, as well as accounting for the loss of an early >1bar CO2 atmosphere. For example, the recent crater wall slumps observed by the Mars Global Surveyor could potentially be explained as alkaline spring extrusions from subsurface carbonation processes.

Objectives of the present research

1.) Conduct detailed petrographic observational analysis of terrestrial carbonation from collected samples of the Oman and Californian ophiolites, comparing the results with data available for Martian meteorites.

2.) Conduct chambered carbonation experiments on terrestrial ophiolite samples using a variety of mineralogical compositions under incrementally increased CO2 pressures, repeating with increasing ratios of CO2/SO2 mixtures.

3.) The results of objectives 1 and 2 will be synthesised to create a quantitative Martian CO2 model with variable parameters of atmospheric compositions, pressures and crustal compositions.

4.) Further mineralogical evidence to validate the model will be sought using the Curiosity Rover's Mars Science Laboratory, and collaborating with partners, new tools (rock polishing and deep drilling capabilities) will be designed, built and tested for planned use on future rovers.


Alt, J. &, Teagle, D. (1999). The uptake of carbon during alteration of ocean crust. Geochimica et

Cosmochimica Acta 63, 1527-1535.

Blank, J, Green, S, Blake, D, Valley, J, Kita, N, Treiman, A, & Dobson, P. (2009). An alkaline

spring system within the Del Puerto Ophiolite (California, USA): A Mars analog site. Planetary

and Space Science 57, 533-540.

European Space Agency (ESA) (2006). Pasteur instrument on ExoMars - artist's impression.

Available: http://spaceinimages.esa.int/Images/2005/02/Pasteur_instrument_on_ExoMars_-

_artist_s_impression. Last accessed 15th November 2013.

Fernández-Remolar, D, Sánchez Román, M, Hill, A, Gómez-Ortíz, D, Ballesteros, O, Romanek, C,

Amils, R. (2011). The environment of early Mars and the missing carbonates. Meteoritics &

Planetary Science 46, 1447-1469.

Gislason, S, Wolff-Boenisch, D, Stefansson, A, Alfredsson, H, Oelkers, E, Gunnlaugsson, E,

Sigurdardottir, H, Sigfusson, B, Aradottir, E, Broecker, W, Matter, J, Stute, M. & Axelsson, G.

(2010). Mineral seqestration of CO2 in basalt - The CarbFix project. Geochimica et

Cosmochimica Acta 74, A336.

Kelemen, P, Hirth, G. (2012). Reaction-driven cracking during retrograde metamorphism: Olivine

hydration and carbonation. Earth and Planetary Science Letters 345, 81-89.

Kelemen, P, Matter, J, Streit, E, Rudge, J, Curry, W. & Blusztajn, J. (2011). Rates and

Mechanisms of Mineral Carbonation in Peridotite: Natural Processes and Recipes for

Enhanced, in situ CO2 Capture and Storage. Annual Review of Earth and Planetary Sciences,

Vol 39, 39, 545-576.

Martinez, G, & Renno, N. (2013). Water and Brines on Mars: Current Evidence and Implications

for MSL. Space Science Reviews 175, 29-51.

NASA. (2006). NASA Images Suggest Water Still Flows in Brief Spurts on Mars. Available:

http://www.nasa.gov/mission_pages/mars/news/mgs-20061206.html. Last accessed 15th

November 2013.

Niles, P.B. & Michalski, J.R. (2011). Evolution of CO2 and H2O on Mars: A cold early history? Lunar

and Planetary Science 42, 2471.

Oehler, D. & Allen, C. (2012). Giant Polygons and Mounds in the Lowlands of Mars: Signatures of

an Ancient Ocean? Astrobiology 12, 601-615.

Phillips, R.J., Davis, B.J., Tanaka, K.L., Byrne, S., Mellon, M.T., Putzig, N.E., Haberle, R.M.,

Kahre, M.A., Campbell, B.A., Carter, L.M., Smith, I.B., Holt, J.W., Smrekar, S,E., Nunes, D.C.,

Plaut, J.J., Egan, A. F., Titus, T.N. & Seu, R. (2011). Massive CO2 ice deposits sequestered in

the South polar layered deposits of Mars. Science 332, 838-841.

Taylor, G, Martel, L, Karunatillake, S, Gasnault, O. & Boynton, W. (2010). Mapping Mars

geochemically. Geology 38, 183-186.

Tomkinson, T, Lee, M, Mark, D, Stuart, F. (2013). The Nakhlite meteorites provide evidence for

mineralisation of Martian CO2 by carbonation of silicates. 44th Lunar and Planetary Science


By Science Hooker, Mar 24 2016 01:12PM

A scribble I did that won the 15th Word Hut writing competition (2015)

Amina sat alone with her thoughts, swimming in them like bitter sweet syrup. The tension formed by a quiet rustling maelstrom of pressurised emotion and well camouflaged feelings uncoiled and stretched by the warmth and safety of the solitude.

The bruises danced, twirled and pirouetted in wild style spanning ankles to forehead, painting her like some tattooed Māori, the violent freshness of some juxtaposed the dusked whispers of others, tales of bygone force; the tattooist worked in stages.

There was no weeping. Tears did not accompany her into this obscure martyrdom, at least not for long. Such pleasant acts of healing catharsis had long since evaporated from her soul and only the dry ache remained, deep in her chest, like a baby bird, wanting out.

She could leave, of course. She wasn’t incapable, nor too weak to stand up to her tormentor. Help lines and social workers abounded. No shortage of charities greedily feasted upon such pristine samples of abused wretchedness, like vultures squabbling for ownership of the righteous indignation available. Crosses, Aums, wheels and waning moons all vying with each other replete with advertising and cross marketing to preen their sense of worth by acting as saviour. The power of philanthropy by definition contains power hence invariably attracting rank upon serried rank of broken and hungry aspirant heroic liberators, junkies desperately craving the ego hit that mercy and benevolence temporarily deliver. No. Her energy and worth were devoured enough, without inviting more to the table.

Even Pavlov underestimated the nature of sound. A purring engine and chattering gravel instigated unchecked spinal shivers, dread weights thudding once again upon her mind. She needn’t even peek through netted drapes to know it was him, HIM, though she looked nevertheless, if only to reassure that her daughter Hanaâ was with HIM. She was all that mattered in this terrible, brutal equation of people. The imminent return hastened her mind to coalesce and clamber ungainly from the pool of reverie it had been wallowing in, dripping sticky puddles of remnant thought upon the hard floor of reality as she swiftly towelled and daubed her inner self to numb repose before the door opened and it all came flooding in.

A tagine was simmering on the stove, tantalising wafts of cooked olive, lemon, prune and chicken converged with the delightful pungency of freshly baked wholemeal bread. It wouldn’t help. It would not ameliorate the coming wave. Defence lay in resignation only, of adept non-provocation. Hard gained experience demonstrated that cheery greetings in the face of hostility were futile, and that the best she could hope for was muted inanimateness and unnoticed utility; for furniture at least is rarely hated to vicious excess. It never worked though. Her responses, however muffled, would invariably draw ire and wrath.

As the tattooist began HIS work in earnest, a child scurried to sit in her wardrobe as was her want during these incomphrehensible spectacles of adult ritual. Unchangingly familiar icons floated upon the white ghostly glare of a smart phone, the permanence of the branding providing an absurd yet remarkably effective succour to the unstable chaos of life beyond the wardrobe door. The ability to ‘like’ something or not was reassuring testament that her thoughts upon things mattered; the crashes and thuds next door notwithstanding. Hanaâ still missed Morocco with passion, and had never wanted, never chose, any of this. No one had asked her. No one had asked if she wanted to come to a place where the sun had died amidst the perennial drizzle. No one had asked if she liked the man who had so rudely seized upon her world, with his whirlwind of money and promises. Anger intertwined with resentment and marinated on a slow simmer towards her mother’s conviction that passports, schools and futures outweigh sunshine, friends and a joyful present. It burnt her feelings, scorching away smiles to hear that all this extant hell was for her benefit. The idea that being snatched away to faraway lands by a monster would be ‘worth it’ for all the wonderful things she would go on to achieve in life placed a burden of such fearful grandness upon her wings that they had snapped off without anyone realising; a baby bird fallen from the nest.

As the storm abated, ebbing to rippled eddies of malice that softly permeated the house like a smell, Amina and Hanaâ nestled on the couch, cradling in limp embrace and ignoring the winces when clumsy comforting fingers touched too vigorously upon the impact sites of swelling burgundy. HE sat slumped in HIS chair, Lord and owner of this microcosm; and upon a resilient non-woven polypropylene foam throne nursed a knuckle grazed from HIS justice, the remote control substituting as sceptre.

The television flickered into motion with a buzzing hum, drawing in all souls and wandering thought patterns into its theatre of carefully managed news, stories and violence; modernity’s Roman coliseum. The news story was rotating the same images like a mantra of carnage. Terrorist suicide bombers had unleashed their deadly swan songs in the capital. The anchor instructing they were insane manifestations of distilled evil fanatically seeking martyrdom for their false cause by attacking the pillars of global civilisation and goodness, embodied by the downtown corporate elite; that we should not deterred, nor lose hope in our idyll of hegemonic harmony by such savage statements of dissent.

Amina pondered on what the penultimate thoughts of a suicide bomber must feel like. There must be excitement. Adrenaline, fear, righteousness, yet perhaps with just a tantalising taste of uncertainty, like a gambler working a big hand. The exaltedness of believing with sincerity that death, and by inference one’s life, was an act of sacrifice to some great cause and therefore of important significance. The comfort of faith imbedded in the security of never needing to later account for the deed. The consequences instant, simple and dramatically grand. Yes, she concluded bitterly, some martyrs have it easier than others.

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