25 August 2009

Flyover on Triton - Voyager +20 Years

Twenty years is a long time, but that is how long its been since Voyager 2 completed its primary mission during a close pass of the planet Neptune. The planet's largest Moon would steal much of the thunder. I myself was a relatively new post-doctoral researcher working at Jet Propulsion Lab, where I had been an intern 10 years earlier during the Voyager 2 Jupiter encounter. I was not part of the Project at that time, but a friend escorted me and another friend into the imaging control center to watch as the Triton images came in. We weren't really supposed to be there I guess and no doubt we ruffled a few feathers but I doubt many would truly begrudge us the experience.

In those days lab workers could watch the mission unfold as each new image of Neptune and its storm clouds flashed on our monitors. Each day it grew larger and more detailed. Triton was the real mystery as even a week before the big August 25th encounter, the actual size of this cold moon was still unknown! The first high resolution images of Triton flashed on the screens and everyone could see that the surface was geologically complex and very young. There were very few craters on the surface (its age is still uncertain but is likely even younger than that of ocean-covered Europa and most of Enceladus). Long ridges, volcanic craters and an odd terrain that looked remarkably like the skin of a cantaloupe marked the surface.

To this day, Triton's surface looks alien and unlike any we have seen elsewhere. Much of this is related to the ice-rich composition, with water, methane, nitrogen, CO, CO2, and other ices in abundance. Triton is likely a captured Kuiper Belt object and residual heat from that event has keep it very warm inside. There may evn be an ocean beneath its surface. Triton bears some remarkable similarities to Pluto but we will have to wait until summer 2015 to find out iif the two bodies look even remotely similar. Nonetheless, there are still things to be learned about Triton from 20 year old data. One of those is the topography of the surface. I have put together a new topographic map of the surface and used it to make a flyover movie simulating the navigations of a vehicle a few thousand kilometers above the surface. A word of warning, the surface of Triton does not have mountains higher than a mile so you will not see towering volcanoes like on Mars or deep basins like on the Moon. What you can see is a complex landscape scarred by small ridges, mounds and pits, many of which are volcanic in origin. There are even a few small impact craters, as well as walled volcanic plains. [By the way, Wikipedia is not entirely correct. The diapir hypothesis for cantaloupe terrain originated with Schenk and Jackson, in Geology, 21, 299, 1993!]

The video begins near the western edge of Neptune-facing hemisphere with an approach over cantaloupe terrain and two large smooth walled plains. The video tracks due east for roughly 1500 kilometers over a large province of volcanic pits, calderas and smooth plains. The video was produced from using a new topographic map of Triton, combined with a 1.65-kilometer resolution image mosaic. Topographic mapping was based on shape-from-shading analysis of the original Voyager images. Data such as these are being used to help plan New Horizons encounter with Triton's estranged twin Pluto in 2015.

Vertical relief has been exaggerated by a factor of ~25 to aid interpretation. It has been formatted to be iPod and iPhone compatible, and can also be downloaded at www.unmannedspaceflight.com and the NASA Photojournal. Additional still images from the movie can be found in the second post to this blog and on the NASA Photojournal.

All Images Credit: NASA/JPL and Paul Schenk, Lunar and Planetary Institute.
Use is not restricted, but a request for use (or for a quality digital copy) should be forwarded to the author. Proper credit is always appreciated!

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