Global Warming on Pluto Puzzles Scientists
SPACE.com ^ | October 9, 2002 | Robert Roy Britt

Posted on 01/23/2007 10:24:01 AM PST

The sun has been warmer over the last few decades and as such has been heating up all the planets in the solar system – data is coming in verifying that this trend is on all planets and not just earth as the Global warming people have suggested for almost a decade now.

Global Warming on Pluto Puzzles Scientists By Robert Roy Britt Senior Science Writer posted: 09 October 2002 01:25 p.m. ET

In what is largely a reversal of an August announcement, astronomers today said Pluto is undergoing global warming in its thin atmosphere even as it moves farther from the Sun on its long, odd-shaped orbit.

Pluto's atmospheric pressure has tripled over the past 14 years, indicating a stark temperature rise, the researchers said. The change is likely a seasonal event, much as seasons on Earth change as the hemispheres alter their inclination to the Sun during the planet's annual orbit.

They suspect the average surface temperature increased about 3.5 degrees Fahrenheit, or slightly less than 2 degrees Celsius.

Pluto remains a mysterious world whose secrets are no so easily explained, however. The warming could be fueled by some sort of eruptive activity on the small planet, one astronomer speculated.

The increasing temperatures are more likely explained by two simple facts: Pluto's highly elliptical orbit significantly changes the planet's distance from the Sun during its long "year," which lasts 248 Earth years; and unlike most of the planets, Pluto's axis is nearly in line with the orbital plane, tipped 122 degrees. Earth's axis is tilted 23.5 degrees.

Though Pluto was closest to the Sun in 1989, a warming trend 13 years later does not surprise David Tholen, a University of Hawaii astronomer involved in the discovery.

"It takes time for materials to warm up and cool off, which is why the hottest part of the day on Earth is usually around 2 or 3 p.m. rather than local noon," Tholen said. "This warming trend on Pluto could easily last for another 13 years."

Stellar observations

The conclusion is based on data gathered during a chance passage of Pluto in front of a distant star as seen from Earth. Such events, called occultations, are rare, but two of them occurred this summer.

In the occultations, which are like eclipses, astronomers examined starlight as it passed through Pluto's tenuous atmosphere just before the planet blotted out the light.

The first occultation, in July, yielded limited data because of terrestrial cloud cover above key telescopes. Marc Buie, an astronomer at Lowell Observatory, scrambled to observe the event from northern Chile using portable 14-inch (0.35-meter) telescope. Afterward, Buie said he was baffled by what seemed to be global cooling of Pluto's atmosphere punctuated by some surface warming.

Then on Aug. 20, Pluto passed in front of a different star. The latter event provided much better data captured by eight large telescopes and seems to clarify and mostly reverse the earlier findings.

The results were compared to studies from 1988, the last time Pluto was observed eclipsing a star.

James Elliot of MIT led a team of astronomers who coordinated their observations and presented the findings today at the annual meeting of the American Astronomical Society's (AAS) Division for Planetary Sciences in Birmingham, Ala.

Elliot said the Aug. 20 occultation was the first that allowed such a deep probing of the composition, pressure and the always-frigid temperature of Pluto's atmosphere, which ranges from -391 to -274 degrees Fahrenheit (-235 to -170 degrees Celsius).

Volcanoes on Pluto?

Elliot hinted at the possibility of another factor fueling Pluto's warming trend.

He compared Pluto to Triton, a moon of Neptune. Both have atmospheres made mostly of nitrogen. In 1997, Triton occulted a star and astronomers found that its atmosphere had warmed since the last observations were made in 1989 during the Voyager mission. Back then, Voyager found dark material rising above Triton, indicating possible eruptive activity.

"There could be more massive activity on Pluto, since the changes observed in Pluto's atmosphere are much more severe," Elliot said. "The change observed on Triton was subtle. Pluto's changes are not subtle."

There is no firm evidence that Pluto is volcanically active, but neither is there evidence to rule out that possibility. Even the Hubble Space Telescope can barely make out Pluto's surface.

Elliot added that the process affecting Pluto's temperature is complex. "We just don't know what is causing these effects," he said.

Let's go there

Elliot and others believe this poor understanding of our solar system's tiniest planet is grounds for sending a robot to investigate. Pluto is the only planet not visited by a spacecraft.

NASA has shelved a mission that would explore Pluto and the Kuiper Belt of frozen objects in which it resides.

Congress, however, appears to view the mission as worthy of some funds. A House budget panel this week followed the lead of the Senate in approving $105 million for the mission. If final approval comes, NASA would be compelled to undertake the project.

Interestingly, while Pluto's atmosphere has been growing warmer in recent years, astronomers have argued that a Pluto mission must launch by 2006, lest it miss the opportunity to study Pluto's atmosphere before it completely freezes out for the winter.

Tentative mission plans call for a robotic probe that would not reach Pluto for several years, making a flyby sometime prior to 2020 prior to investigating other objects deeper in the solar system.

Meanwhile, astronomers are looking forward to a space telescope called SOFIA, slated to begin operations in 2004. SOFIA will carry an instrument designed specifically to observe occultations and is expected to be employed when Pluto passes in front of other stars in coming years.

The Pluto observations this summer were funded by NASA, the Research Corporation and the National Science Foundation. Observations were made using the telescopes at the Mauna Kea Observatory, Haleakala, Lick Observatory, Lowell Observatory and the Palomar Observatory.

Global Warming Detected on Triton (Neptune's Moon)
Science a GoGo (quoting MIT Professor James Elliott) ^ | 28 June 1998 | Science a GOGO

Posted on 01/23/2007 10:19:54 AM PST by Moseley

28 June 1998 Global Warming Detected on Triton There may not be much industrial pollution on Neptune's largest moon, but things are hotting up nonetheless...

The Earth is not alone in suffering global warming. According to observations made by NASA's Hubble Space Telescope and several ground-based instruments, temperatures on Neptune's largest moon have increased dramatically since the Voyager space probe swung by in 1989. So much so, in fact, that Triton's surface of frozen nitrogen is turning into gas, making its thin atmosphere denser by the day.

"At least since 1989, Triton has been undergoing a period of global warming," confirms astronomer James Elliot, professor of Earth, Atmospheric and Planetary Sciences at Massachusetts Institute of Technology. "Percentage-wise, it's a very large increase."

Elliot and colleagues from the Lowell Observatory and Williams College report their findings in the June 25 issue of the journal Nature. Triton's 5 percent increase on the absolute temperature scale from about -392 to -389 degrees Fahrenheit would be like the Earth experiencing a jump of some 22 degrees Fahrenheit in just nine years.

There are two possible explanations for the moon's warmer weather. One is that the frost pattern on Triton's surface may have changed over the years, absorbing more and more of the sun's warmth. The other is that changes in reflectivity of Triton's ice may have caused it to absorb more heat.

About the same size and density as Pluto, Triton is thirty times as far from the sun as the Earth. It is known to be extremely cold and gusty, with wind speeds close to the speed of sound. Its atmosphere is composed mostly of molecular nitrogen, and its terrain varies between icy regions and bare spots. Quips Elliot: "When you're so cold, global warming is a welcome trend."

Picture courtesy of NASA/JPL