Still waters run deep

Whoop! Today I was finally accepted onto the City University science journalism MA. After reading countless articles these days about the failing newspapers, graduate competition and lack of positions opening I'm really hoping this will give me the edge in future job markets! I think my place was won solely on my Geoscientist internship and the experience it gave me, let's hope it's worth the £8000 fees. My next article for the magazine is published here first, exclusive to my blog, for the time being at least. Enjoy!


Still waters run deep


In 1911 a meteorite from Mars hurtled towards North Africa, splitting into forty small pieces, and (legend has it) killing a dog. Harriet Jarlett reports.


Geoscientist Online 23 February 2011

Vein of martian clay and carbonate

Exactly a century after the first nakhlite meteorite was discovered in El-Nakhla, Egypt, the same meteorite is being used to discover how water may have flowed on Martian surfaces1. (together with other samples from Lafayette, Yamoto and Governador Valadares meteorites).


The Nakhla meteorite is a rare type of meteorite, being a sample of the planet Mars that was splashed off the surface of the red Planet by another meteorite impact. Mars, having a much lower gravitational pull than the Earth, requires a much smaller impact to force ejecta out of its gravity well, and into interplanetary space. Some of these escaped ejecta then find their way towards the Earth.


Scientists from the University of Leicester’s Space Research Centre milled micron-thin slices off the martian meteorite fragments and examined them under the electron microscope in an attempt to understand the hydrothermal processes which formed the secondary minerals infilling some prominent veins.


The veins formed when a brine flowed through the rock (a lava) while it was still part of its parent planet. These veins were already known to have contained ice, carbonate and clay minerals in amounts corresponding to their depth below martian surface (the shallower meteorites contain soluble salts)2, which formed during the impact that sent them hurtling towards the Earth.


Changela and Bridges suggest the fluid came from an underground source, such as permafrost; and since deeper nakhlites, like Lafayette, show greater amounts of alteration Changela and Bridges realised that the water had not percolated downwards from the planet surface but instead flowed upward, like water rising from an aquifer to a source spring.


Changela suggests that an impact shock caused the minerals to fracture, and the subsurface permafrost to melt and flow through nearby rock. Dr Bridges, who is supervisor to Hitesh Changela’s PhD, explains the importance of this discovery: “We are now starting to build a realistic model for how water-deposited minerals formed on Mars, showing that impact heating was an important process.”

Martian serpentine atomic layers

Bridges and Changela have been able to identify what size of impact would be needed to form such a hydrothermal system, and can match this to the age and hemisphere in which the nakhlites were born. They have then been able to model how much fluid was likely to have been formed, and how long the system lasted for (one to 10 months).


This discovery comes soon after Mars orbiters revealed carbonate and phyllosilicates on the surface of the planet, such as those found in the Nili Fossae region, where surface fluvial activity and shallow lake deposits may have resulted in carbonate formation3. Clay minerals identified in the walls of impact craters suggest local hydrothermal systems created by impacts are common to the Martian surface.


Further reading:
Alteration assemblages in the nakhlites: Variation with depth on Mars (pp 1847–1867)H G CHANGELA and J C BRIDGES Meteoritics & Planetary Science 45, Nr 12, 1847–1867 (2011) Article first published online: 6 JAN 2011 | DOI: 10 1111/j 1945-5100 2010 01123

Love makes the world go round...

...And makes missions successful! February is the month for all things love related and whilst some of our Valentine's were disastrous for NASA's Stardust mission February 14th 2011 turned out to be full of romance.

Space has rarely left the news recently, in particular with the Kepler telescope discovering new, Earth-like planets and the exciting simulated walk on the red planet with the Mars500 project. One of the most exciting discoveries came yesterday when Stardust came within 180km of the comet, Tempel 1. Sending 72 images back to NASA and numerous details about the comet's dust, Stardust will be able to provide great insight into how these huge balls of ice and dust change over time. Comets are thought to contain frozen primordial ingredients that date back to the birth of the solar system some 4.5 billion years ago, information about them could provide us with clues to how the planets and stars form.



Images taken through the day of Tempel 1 by Stardust,

Not only did Nasa have cause for great celebration after the success of their mission, but a scientist working on the project made sure this was a Valentine's day not to forget. Steve Chesley, of NASA's Near-Earth Object Program office was presenting data about the mission and slipped an extra powerpoint slide into the presentation reading 'Will you marry me?'
 

The Stardust mission has provided some fascinating insight into the inner workings of the comet, by imaging the surface. It's bigest achievment is  providing data on what happened when, in 2005, the Deep Impact sent a less-than-romantic impactor hurtling into the comet. The crater this impact left has a small mound in the centre which suggests that some of the ice which was thrown up in the collision came straight back down. Pete Schultz of Brown University explained the "cometary nucleus is fragile and weak based on how subdued the crater is we see today". He went on to explain that because of the frayed edges of the crater it is obvious the surface has changed since the impact, " the crater partly healed itself." Erosion features, newly formed pits and holes were visible on the surface, clearly altered compared to images sent back from Deep Impact. These all form as the comet moves closer to the sun, causing ice to evaporate off of the surface and form the dust 'tail' of the comet.



This isn't the first time Stardust has given NASA a present on V-day. In 2006 analysis of data sent back from the comet showed some of the comet particles to be heart shaped!



Heart-shaped comet particle extracted from aerogel - http://stardust.jpl.nasa.gov/news/status/060221.html