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  • IJsmaantje Iapetus gesnapt

    - Dankzij klimaatonderzoek gaan we Saturnus’ vreemde maan Iapetus ineens veel beter begrijpen. Die ijsklomp kent een heel lichte en heel donkere kant, zoals al in 1671 was gezien. Microgolven-tests op aarde leren nu wat zulk ijs op dat maantje veroorzaakt.

    Paul Ries, een graduate student aan de University of Virginia en radioastronoom, vertelt op Space.com over zijn recente ontdekking. "What makes Iapetus unusual is that it has one side that is dark and one side that is bright. What I found was that the emissions were what we call flat, which means that as you go from one radio wavelength to another, the emissions were the same when you expect them to be declining."

    IJs en zout veranderen radioecho's

    "What that corresponds to is a very steep absorption. I was expecting to find something, but I was not expecting to find something quite so strong." Toen ging hij kijken naar het werk van zijn radio-onderzoek instituut hier op aarde. "It turns out that there's a lot of work in climate science with modeling the radio emissions from Earth at a wide range of wavelengths."

    "This is important to astronomers because they're at wavelengths that are transparent, where you don't have too much interference from the atmosphere. My thought was: why not try to use the icy surfaces on Earth to model icy surfaces on bodies in the outer solar system?"

    "Salinity content changes the microwave emission properties of oceans," Ries said. "The other area of interest is icy surfaces, which can vary depending on the structure of the ice. If there's melting, the signature changes drastically, which is why climate scientists have done some extensive studies of emissivity variations in the microwave spectrum."

    Meten tot in het ijs achter Pluto

    Maar ijs op aarde, ronde de polen en in ijsbergen op de oceanen is natuurlijk iets anders dan het ijs dat op planeten en manen elders in het zonnestelsel aan de oppervlakte zit. "You can't have liquid water on a body with no atmosphere, which is what we think of Iapetus. If there's any gas hanging around, it's not hanging around for long. That's true for most of the icy bodies in the outer solar system. You don't expect them to have an atmosphere, so there's no liquid water involved."

    Deze aspecten verwerkt Ries nu in zijn model om het ijs buiten onze aarde, tot in de grondstof voor de kometen in de 'Kuijper Belt' achter de planeet Pluto te analyseren en modellen te ontwikkelen die hun gedrag en werkelijkheid veel dichterbij brengen.

    "In the specific case of Iapetus, it can help shed light on what's going on in its formation and evolution. Iapetus certainly has some strange stuff that needs to be explained, so this is potentially very interesting for the future. But eventually, I'd like to do observations of the outer solar system - the Kuiper Belt and beyond."