Monthly Archives: February 2016

New open access paper by me: Oxygen in the Earth’s mantle

Triple oxygen isotopic composition of the high-3He/4He mantle

Published Open Access in Geochimica et Cosmochimica Acta, Volume 176, 1 March 2016, Pages 227–238.

I promise to write an explainer on this research soon because I realise the title of the paper is not particularly friendly to non-specialists (to say the least). This project relates to work I was doing during my PhD, looking deep into the Earth’s mantle by analysing samples of ancient volcanoes, but I just couldn’t leave it behind. Because I’m a geochemist I like to try to analyse every element I can, and we hadn’t done oxygen isotopes in these samples so a few years later it’s now done. There is of course a good reason for wanting to analyse oxygen but I’ll explain more when I write my ‘explainer’ blog. There are quite a few authors involved in this work, based across Europe and the USA, so it’s been a tricky project to manage in terms of time zones and opinions, but we got there in the end, particularly after a huge amount of detailed lab work by some of my co-authors (thank you Richard!). It’s so nice to finally see the paper out for the community to read, hopefully they like it!

Beautiful protoplanetary disk captured by ALMA

Image taken by ALMA of the Sz 91 star. More info: http://www.almaobservatory.org/en/press-room/press-releases/925-alma-confirms-predictions-on-the-interaction-between-protoplanetary-disks-and-planets
Image taken by ALMA of the Sz 91 star. More info: http://www.almaobservatory.org/en/press-room/press-releases/925-alma-confirms-predictions-on-the-interaction-between-protoplanetary-disks-and-planets

Another beautiful image has been released by the ALMA (Atacama Large Millimeter/Submillimeter Array) telescope of a protoplanetary disk (see above), but in this one there appears to be evidence for newly-forming planets interacting with their disk. The star system we’re looking at is called Sz 91 and it is 650 light years from Earth. The bright coloured ring that can be seen in the image is a relatively dense and cold dust ring, which is exciting in itself, but the hole in the middle is thought to have been carved out by the formation of some hot gas giant planets. During the formation of the protoplanetary disk, dust and gas migrate inwards towards the central star, and so the forming planets act to stop this movement into the inner parts of the disk. The dust on the outside of the ring still migrates in because of gravitational and aerodynamic forces, hence we get an accumulation of dust in the ring as seen here. The results suggest that the ring is primarily composed of mm-sized particles, and these are expected to eventually form into planets.

It’s really nice for a comet scientist like me to see images such as this because it gives me a glimpse of what our Solar System might have looked like 4.6 billion years ago, a time we can’t otherwise get to (unless someone invents time travel – and even then I’m not sure it’s a particularly welcoming environment we’d want to visit!). The only way we can access this time in our Solar System’s history is to analyse comets because they sample this exact era. But the problem then is that we have to piece together a picture of what it looked like using only chemical analyses, this isn’t easy but we try our best. This is why, despite the fact I’m not an astronomer, I still find these ALMA images fascinating and they can help to shape the theories I put forward in my work that are based on my chemical comet data.

Credit: ALMA (ESO/NAOJ/NRAO) http://www.almaobservatory.org/press-room/press-releases/771-revolutionary-alma-image-reveals-planetary-genesis
Credit: ALMA (ESO/NAOJ/NRAO)
http://www.almaobservatory.org/press-room/press-releases/771-revolutionary-alma-image-reveals-planetary-genesis

As an aside, my interest in ALMA first stemmed from another of its beautiful images of a protoplanetary disk around the star HL Tau (see above). In this one we see gaps in the dust ring itself which we are told points to the fact that ALMA has caught a picture of this disk at the time when the planets are forming. The young planets are literally clearly their orbit, this is very exciting to see and it is also happening much earlier than we expected, this image is captured when the disk is only 1 million years old. The level of detail in this image is astounding, especially when you consider that this is 450 light years away.