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."