Water, Mars & Herschel (everyone else can, why can’t we?)

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The first set of results from the Herschel Space Telescope have been flooding out over the past couple of weeks*, so it’s about time they got a mention here. Rather than rehashing one of the many press releases, I thought I’d focus on an interesting result that I doubt will get much attention – the detection of water vapour (and carbon monoxide) on Mars with the spectrometer within the SPIRE instrument.

I have to be upfront about this; the reason why you probably won’t hear much about this is that detecting water on Mars, whilst important for understanding its water cycle, is nothing new, though it is only present in small amounts (900 parts per million according to these observations). It was first seen in the Martian atmosphere in 1963, and since then has been extensively studied with many different observatories. The Opportunity rover even sent back images of cirrus clouds that are very similar to those we see here on Earth:

So what is special about these Herschel observations? Well, the telescope was never expected to be able to make them, because Mars is around 100 times brighter than SPIRE was designed to cope with. (Imagine taking a picture with your digital camera in the direction of the Sun on a really sunny day – the image you get looks overexposed because the excess light has overloaded (saturated) it.) However, the instrument team, led by Bruce Swinyard, didn’t let that stop them – they found a way to ‘desensitize’ the detectors in the instrument and avoid this saturation problem, enabling the water vapour to be seen.

This might not be as flashy as some of the other early results from Herschel but it does illustrate how well its been performing over this first year. This new ‘bright source’ mode will open up new targets to observe that were previously thought impossible and personally I think that’s something worth mentioning!

* For more Herschel results have a look at this audio slideshow from the BBC. There’s also this movie from the European Space Agency celebrating Herschel’s first year in space:

Image credits: NASA

B. M. Swinyard, P. Hartogh, S. Sidher, T. Fulton, E. Lellouch, C. Jarchow, M. J. Griffin, R. Moreno, H. Sagawa, G. Portyankina, M. Blecka, M. Banaszkiewicz, D. Bockelee-Morvan, J. Crovisier, T. Encrenaz, M. Kueppers, L. Lara, D. Lis, A. Medvedev, M. Renge, S. Szutowicz, B. Vandenbussche, F. Bensch, E. Bergin, F. Billebaud, N. Biver, G. Blake, J. Blommaert, M. de Val-Borro, J. Cernicharo, T. Cavalie, R. Courtin, G. Davis, L. Decin, P. Encrenaz, T. de Graauw, E. Jehin, M. Kidger, S. Leeks, G. Orton, D. Naylor, R. Schieder, D. Stam, N. Thomas, E. Verdugo, C. Waelkens, & H. Walker (2010). The Herschel-SPIRE submillimetre spectrum of Mars to appear in the Herschel Special Issue of Astronomy & Astrophysics arXiv: 1005.4579v1

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