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New Horizons for Pluto

I reference my SURF topic in my post about SURF proposals, but I thought I’d elaborate more on what I’ll be doing here, while I wait for April 1 to hear whether my proposal has been accepted.

Albedo describes what fraction of the light that hits a surface is reflected. While this depends on the frequency of the light, we usually talk about average albedo. For icy planets and asteroids, we can measure albedo to ascertain how much ice is on the surface. We can do better by plotting a light curve: an object’s albedo with respect to time as its phase relative to the Earth changes. Since ice usually isn’t distributed evenly over a body’s surface, the albedo varies as the relative orientations of the body to the Earth changes. (Note that we also need to account for the relative position of the Sun because more light will hit the body’s surface when it’s closer to the sun.) By comparing light curves from year to year, we can predict whether the ice distribution is changing or static.

Triton, Neptune’s largest satellite, is much like Pluto in terms of its physical, chemical, and orbital characteristics. Both Triton’s changing light curves and Voyager’s photographs of Triton indicate that ice on Triton’s surface is dynamic. Volatile transport is the technical term for the changing ice distribution.

Some of the dark spots on Triton in this picture may even be cryovolcanoes that erupt water, methane, or ammonia. We don’t know whether volatile transport of this or other forms occurs on Pluto. Most data supports a static model of Pluto’s surface, but a lightcurve collected recently doesn’t fit with this picture.

Is this lightcurve an outlier, or an indication? That’s what I’m going to find out! I’m going to use one of the Table Mountain Observatory telescopes to help my mentor plot a lightcurve for 2013. We want to make a prediction as to what types of things NASA’s New Horizons mission might see when it encounters Pluto in 2015.

Ariel O’Neill