Spring on Titan Brings Sunshine and Patchy Clouds

False-color image of cloud cover dissolving over Titan's north pole and clouds appearing in the southern mid latitudes.

September 21, 2010

The northern hemisphere of Saturn's moon Titan is set for mainly fine spring weather, with polar skies clearing since the equinox in August last year. The visual and infrared mapping spectrometer (VIMS) aboard NASA's Cassini spacecraft has been monitoring clouds on Titan regularly since the spacecraft entered orbit around Saturn in 2004. Now, a group led by Sébastien Rodriguez, a Cassini VIMS team collaborator based at Université Paris Diderot, France, has analyzed more than 2,000 VIMS images to create the first long-term study of Titan's weather using observational data that also includes the equinox. Equinox, when the sun shone directly over the equator, occurred in August 2009.

Rodriguez is presenting the results and new images at the European Planetary Science Congress in Rome on Sept. 22.

Though Titan's surface is far colder and lacks liquid water, this moon is a kind of "sister world" to Earth because it has a surface covered with organic material and an atmosphere whose chemical composition harkens back to an early Earth. Titan has a hydrological cycle similar to Earth's, though Titan's cycle depends on methane and ethane rather than water.

A season on Titan lasts about seven Earth years. Rodriguez and colleagues observed significant atmospheric changes between July 2004 (early summer in Titan's southern hemisphere) and April 2010 (the very start of northern spring). The images showed that cloud activity has recently decreased near both of Titan's poles. These regions had been heavily overcast during the late southern summer until 2008, a few months before the equinox.

Over the past six years, the scientists found that clouds clustered in three distinct latitude regions of Titan: large clouds at the north pole, patchy clouds at the south pole and a narrow belt around 40 degrees south. "However, we are now seeing evidence of a seasonal circulation turnover on Titan – the clouds at the south pole completely disappeared just before the equinox and the clouds in the north are thinning out," Rodriguez said. "This agrees with predictions from models and we are expecting to see cloud activity reverse from one hemisphere to another in the coming decade as southern winter approaches."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate, Washington, D.C. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.
 

Mars Rover Opportunity Approaching Possible Meteorite

NASA's Mars Exploration Rover Opportunity used its panoramic camera to capture this view of a dark rock that may be an iron meteorite. Part of the rim of Endurance Crater is on the horizon. Image Credit: NASA/JPL-Caltech/Cornell University

September 21, 2010

PASADENA, Calif. -- Images that NASA's Mars Exploration Rover Opportunity took at the end of an 81-meter (266-foot) drive on Sept. 16 reveal a dark rock about 31 meters (102 feet) away. The rover's science team has decided to go get a closer look at the toaster-sized rock and determine whether it is an iron meteorite.

"The dark color, rounded texture and the way it is perched on the surface all make it look like an iron meteorite," said science-team member Matt Golombek of NASA's Jet Propulsion Laboratory, Pasadena, Calif. Opportunity has found four iron meteorites during the rover's exploration of the Meridiani Planum region of Mars since early 2004. Examination of these rocks has provided information about the Martian atmosphere, as well as the meteorites themselves.

The newfound rock has been given the informal name "Oileán Ruaidh" (pronounced ay-lan ruah), which is the Gaelic name for an island off the coast of northwestern Ireland. The rock is about 45 centimeters (18 inches) wide from the angle at which it was first seen.

Opportunity has driven 23.3 kilometers (14.5 miles) on Mars. The drive to this rock will take the total combined distance driven by Opportunity and its twin, Spirit, to more than 31 kilometers (19.26 miles).

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover mission for the NASA Science Mission Directorate, Washington. Opportunity landed on Mars in January 2004 for what was planned as a three-month mission.

NASA Selects Investigations for First Mission to Encounter the Sun

The Solar Probe Plus spacecraft with solar panels folded into the shadows of its protective shield, gathers data on its approach to the Sun.  

September 02, 2010

PASADENA, Calif. -- NASA has begun development of a mission to visit and study the sun closer than ever before. The unprecedented project, named Solar Probe Plus, is slated to launch no later than 2018.

The small car-sized spacecraft will plunge directly into the sun's atmosphere approximately 6.4 million kilometers (four million miles) from our star's surface. It will explore a region no other spacecraft ever has encountered. NASA has selected five science investigations that will unlock the sun's biggest mysteries, including one led by a scientist from NASA's Jet Propulsion Laboratory, Pasadena, Calif.

"The experiments selected for Solar Probe Plus are specifically designed to solve two key questions of solar physics -- why is the sun's outer atmosphere so much hotter than the sun's visible surface and what propels the solar wind that affects Earth and our solar
system? " said Dick Fisher, director of NASA's Heliophysics Division in Washington. "We've been struggling with these questions for decades and this mission should finally provide those answers."

As the spacecraft approaches the sun, its revolutionary carbon-composite heat shield must withstand temperatures exceeding about 1,400 degrees Celsius (2,550 degrees Fahrenheit) and blasts of intense radiation. The spacecraft will have an up-close and personal view of the sun, enabling scientists to better understand, characterize and forecast the radiation environment for future space explorers.

NASA invited researchers in 2009 to submit science proposals. Thirteen were reviewed by a panel of NASA and outside scientists. The total dollar amount for the five selected investigations is approximately $180 million for preliminary analysis, design, development and tests.

The selected proposals are:

-- Solar Wind Electrons Alphas and Protons Investigation: principal investigator, Justin C. Kasper, Smithsonian Astrophysical Observatory in Cambridge, Mass.

This investigation will specifically count the most abundant particles in the solar wind -- electrons, protons and helium ions -- and measure their properties. The investigation also is designed to catch some of the particles in a special cup for direct analysis.

-- Wide-field Imager: principal investigator, Russell Howard, Naval Research Laboratory in Washington. This telescope will make 3-D images of the sun's corona, or atmosphere. The experiment actually will see the solar wind and provide 3-D images of clouds and shocks as they approach and pass the spacecraft. This investigation complements instruments on the spacecraft, providing direct measurements by imaging the plasma the other instruments sample.

-- Fields Experiment: principal investigator, Stuart Bale, University of California Space Sciences Laboratory in Berkeley, Calif. This investigation will make direct measurements of electric and magnetic fields, radio emissions, and shock waves that course through the
sun's atmospheric plasma. The experiment also serves as a giant dust detector, registering voltage signatures when specks of space dust hit the spacecraft's antenna.

 -- Integrated Science Investigation of the Sun: principal investigator, David McComas of the Southwest Research Institute in San Antonio. This investigation consists of two instruments that will take an inventory of elements in the sun's atmosphere using a mass 
spectrometer to weigh and sort ions in the vicinity of the spacecraft.

-- Heliospheric Origins with Solar Probe Plus: principal investigator, Marco Velli of JPL. Velli is the mission's observatory scientist, responsible for serving as a senior scientist on the science working group. He will provide an independent assessment of scientific performance and act as a community advocate for the mission.

"This project allows humanity's ingenuity to go where no spacecraft has ever gone before," said Lika Guhathakurta, Solar Probe Plus program scientist at NASA Headquarters, in Washington. "For the very first time, we'll be able to touch, taste and smell our sun."

The Solar Probe Plus mission is part of NASA's Living with a Star Program. The program is designed to understand aspects of the sun and Earth's space environment that affect life and society. The program is managed by NASA'S Goddard Space Flight Center in Greenbelt, Md., with oversight from NASA's Science Mission Directorate's Heliophysics Division. The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., is the prime contractor for the spacecraft.