August 25, 2014 | David F. Coppedge

Active Moon Triton Revisited

25 years ago today, Voyager 2 flew by Triton, a moon of Neptune, astonishing scientists with its active geology.

Paul Schenk is a master at bringing out the best of digital space images, giving them a “you-are-there” realism.  Celebrating the 25th anniversary of the Neptune-Triton encounter of August 1989, he has re-rendered Voyager 2’s original three-color images for a new generation, providing a best-ever recreation of the historic flyby that shocked scientists with views of an actively-erupting body of geysers and ice volcanoes.

Triton southern hemisphere

Triton southern hemisphere from Voyager 2, 8/25/89

The story was released by Jet Propulsion Laboratory, which links to Paul Schenk’s “Icy Moons” website at Houston’s Lunar and Planetary Institute, where the one-minute flyby video can be viewed.  In his blog entry “Triton at 25,” Schenk recalls the occasion with pictures of other key scientists who were involved: Linda (Horn) Spilker, Larry Soderblom, Torrence Johnson and others who continue working at JPL on the Cassini Mission at Saturn; also the late Carl Sagan.  Their initial astonishment has not lessened:

In the intervening quarter century and its many discoveries, I think we have tended to forget how strange and exotic Triton really is!  Its effective surface age may be a little as 10 million years, clearly implying that active geology is going on today.  The cantaloupe terrain, which I interpreted back in 1993 as due to crustal overturn (diapirism), hasn’t been seen anywhere else.  The volcanic region with its smooth plains and volcanic pits large and small, is  the size of Texas.  And the southern terrains still defy interpretation.

The recreated images are also timely because of next year’s Pluto encounter (July 14, 2015) by the approaching New Horizons spacecraft:

In a double sense this is fitting, as Triton is a near twin of Pluto. Triton and Pluto are both slightly smaller than Earth’s Moon, have very thin nitrogen atmospheres, frozen ices on the surface (carbon monoxide, carbon dioxide, methane and nitrogen), and similar bulk composition (a mixture of ices, including water ice, and rock. Triton however was captured by Neptune long time ago and has been wracked by intense heating ever since. This has remade its surface into a tortured landscape of overturned layers, volcanism, and erupting geysers.

What will we see at Pluto? Guesses have ranged from active geology to cold and cratered, so we are in for a suspenseful Summer next year! Triton is of importance as it offers clues to what geologic features might look like on Pluto, given that the icy crusts of both bodies are probably rather similar and would presumably react in similar ways under internal stress and heat. So if there were or are volcanoes on Pluto they could look similar to those we see on Triton.

None of these articles mentioned the fact that Triton goes around Neptune in a nearly circular orbit in the wrong (retrograde) direction, making capture a highly improbable event.

Planetfest 1989, Neptune encounter

Public viewing Voyager 2 flyby of Neptune, 8/25/89

25 years ago, 8 years before I went to work at JPL, I took a group of people to the Pasadena Convention Center for a “Planetfest” celebrating the Neptune flyby.  We watched the successful encounter of Neptune on a giant screen.  Later, I was up all night watching the images of Triton arrive on TV in real time as scientists tried to interpret what they were seeing.  Even in the unprocessed images, the scientists could tell something strange was going on.  As you can see from Schenk’s statements, Triton still defies explanation 25 years later.  He guessed an age of 10 million years for the surface, which I think is unjustified extrapolation; even so, 10 million years would represent just 1/450th the assumed age of the solar system.  Combined with the activity found on Io and Enceladus, this causes a serious problem for believers in the consensus age.

In The New Solar System, 4th ed. (1998), after nine years to think about Triton, Dale P. Cruikshank said, “Why so much territory should have so few impacts [craters] is not well understood; there is at least the suggestion that Triton has undergone extensive, geologically recent, and perhaps ongoing resurfacing.”  He also noted that Voyager 2 failed to detect complex hydrocarbons that should have precipitated onto the surface “at a relatively high rate.  Such species have not been detected so far,” he added.  “….The fact that we have not detected these more complex molecules adds strength to the contention that Triton’s surface is both geologically very young (from the absence of large numbers of impact craters) and chemically ‘fresh’”  (pp. 288-289).  The scientists did not expect to see about 100 nitrogen geysers on the southern hemisphere erupting five miles high with 40-mile long trails.  “It came as a great surprise when it was recognized that Voyager 2 had imaged evidence of this airborne transport in action!”  Once again, the predictions of secular scientists were wrong.  “….Voyager’s extreme good fortune has given us a new perspective on a world that was formerly thought to be cold and utterly dead, geologically speaking…. There are no clear answers yet.” (p. 290).  That sounds just like the 2014 status report.  —David Coppedge

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