EPOXI - low cost mission that will expand our knowledge of both cometary bodies and extrasolar planetary systems.

EPOXI Team Develops New Method to Find Alien Oceans

Astronomers have found more than 300 alien (extrasolar) worlds so far. Most of these are gas giants like Jupiter, and are either too hot (too close to their star) or too cold (too far away) to support life as we know it. Sometime in the near future, however, astronomers will probably find one that's just right – a planet with a solid surface that's the right distance for a temperature that allows liquid water -- an essential ingredient in the recipe for life.

But the first picture of this world will be just a speck of light. How can we find out if it might have liquid water on its surface? If it has lots of water – oceans – we are in luck. NASA-sponsored scientists looking back at Earth with the Deep Impact/EPOXI mission have developed a method to indicate whether Earth-like extrasolar worlds have oceans. "A 'pale blue dot' is the best picture we will get of an Earth-like extrasolar world using even the most advanced telescopes planned for the next couple decades," said Nicolas B. Cowan, of the University of Washington. "So how do we find out if it is capable of supporting life? If we can determine that the planet has oceans of liquid water, it greatly increases the likelihood that it supports life. We used the High Resolution Imager telescope on Deep Impact to look at Earth from tens of millions of miles away -- an 'alien' point of view -- and developed a method to indicate the presence of oceans by analyzing how Earth's light changes as the planet rotates. This method can be used to identify extrasolar ocean-bearing Earths." Cowan is lead author of a paper on this research appearing in the August 2009 issue of the Astrophysical Journal. Our planet looks blue all the time because of Rayleigh scattering of sunlight by the atmosphere, the same reason that the sky appears blue to us down on the surface, points out Cowan. "What we studied in this paper was how that blue color changes in time: oceans are bluer than continents, which appear red or orange because land is most reflective at red and near-infrared wavelengths of light. Oceans only reflect much at blue (short) wavelengths," said Cowan.

This narrow-angle color image of the Earth, dubbed 'Pale Blue Dot', is a part of the first ever 'portrait' of the solar system taken by Voyager 1. The spacecraft acquired a total of 60 frames for a mosaic of the solar system from a distance of more than 4 billion miles from Earth and about 32 degrees above the ecliptic. From Voyager's great distance Earth is a mere point of light, less than the size of a picture element even in the narrow-angle camera. Earth was a crescent only 0.12 pixel in size. Coincidentally, Earth lies right in the center of one of the scattered light rays resulting from taking the image so close to the sun. This blown-up image of the Earth was taken through three color filters violet, blue and green and recombined to produce the color image. The background features in the image are artifacts resulting from the magnification.



The maps that the team created are only sensitive to the longitudinal (East - West) positions of oceans and continents. Furthermore, the observations only pick out what is going on near the equator of Earth: the equator gets more sunlight than higher latitudes, and the EPOXI spacecraft was above the equator when the observations were taken. These limitations of viewing geometry could plague observations of extrasolar planets as well: "We could erroneously see the planet as a desert world if it had a nearly solid band of continents around its equator and oceans at its poles," said Cowan. Other things besides water can make a planet appear blue; for example, in our solar system the planet Neptune is blue due in part to the presence of methane in its upper atmosphere. "However, a Neptune-like world would appear as an unchanging blue using this technique, and again it's the changes in the blue color that reveal oceans to us," said Cowan. "There are some weird scenarios you can dream up that don't involve oceans but would lead to varying patches of blue on a planet, but these are not very plausible." "A spectrum of the planet's light that reveals the presence of water is necessary to confirm the existence of oceans," said Drake Deming, a co-author of the paper at NASA's Goddard Space Flight Center in Greenbelt, Md. Instruments that produce a spectrum are attached to telescopes and spread out light into its component colors, like a prism separates white light into a rainbow. Every element and molecule emits and absorbs light at specific colors. These colors can be used like a fingerprint to identify them. "Finding the water molecule in the spectrum of an extrasolar planet would indicate that there is water vapor in its atmosphere, making it likely that the blue patches we were seeing as it rotates were indeed oceans of liquid water. However, it will take future large space telescopes to get a precise spectrum of such distant planets, while our technique can be used now as an indication that they could have oceans," said Deming. The technique only requires relatively crude spectra to get the intensity of light over broad color ranges, according to the team. NASA's Deep Impact made history when the mission team directed an impactor from the spacecraft into comet Tempel 1 on July 4, 2005. NASA recently extended the mission, redirecting the spacecraft for a flyby of comet Hartley 2 on Nov. 4, 2010. EPOXI is a combination of the names for the two extended mission components: a search for extrasolar planets during the cruise to Hartley 2, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact eXtended Investigation (DIXI). The University of Maryland is the Principal Investigator institution, leading the overall EPOXI mission and DIXI. NASA Goddard leads the EPOCh investigation. NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages EPOXI for NASA's Science Mission Directorate, Washington. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

Model of CNOFS CINDI-will study the elements that influence space weather near Earth's equator.

CINDI Hunts Giant, Radio-Busting Plasma Bubbles

This photo shows a scale model of the C/NOFS probe. NASA's CINDI instrument is installed on C/NOFS. Graphic courtesy of the U.S. Air Force



They come out at night over the equator -- giant bubbles of plasma, a gas of electrically charged particles, silently rise in the upper atmosphere. While invisible to human eyes, they can disrupt crucial radio communication and navigation signals, like the Global Positioning System (GPS). NASA is collaborating with the Air Force on a unique investigation that will study how these bubbles form by conducting the Coupled Ion Neutral Dynamic Investigation (CINDI) as part of the payload for the Air Force Communication/Navigation Outage Forecast System satellite.

"Understanding when and where plasma bubbles occur, how severe they will be and how long they will last is vitally important since interference from plasma bubbles affects GPS signals and other radio signals that can travel around the globe by reflection from layers in Earth's upper atmosphere, called the thermosphere and the ionosphere," said CINDI Principal Investigator Prof. Rod Heelis of the University of Texas at Dallas. "These signals are used for communication and navigation by a wide variety of commercial and government entities including the Federal Aviation Administration and search and rescue operations. Most of us are directly or indirectly dependent on the proper function of these space-based systems and it is imperative that we attempt to predict the times when such systems may not be reliable."

Deep Impact -Exploring Comet Tempel 1 to determine the origins of life in our Solar System.

Comet Tempel 1, which created a flamboyant Fourth of July fireworks display in space last year, is covered with a small amount of water ice. These results, reported by members of NASA’s Deep Impact team in an advanced online edition of Science, offer the first definitive evidence of surface ice on any comet.

“We have known for a long time that water ice exists in comets, but this is the first evidence of water ice on comets,” said Jessica Sunshine, Deep Impact co-investigator and lead author of the Science article. Tempel I

The three small areas of water ice on the surface of Tempel 1 appear in this image, taken by an instrument aboard NASA’s Deep Impact spacecraft. Photo credit: NASA.

A chief scientist with Science Applications International Corporation who holds three Brown University degrees, Sunshine said the discovery offers important insight into the composition of comets – small, Sun-orbiting space travelers that are believed to be leftovers from the formation of the solar system.

“Understanding a comet’s water cycle and supply is critical to understanding these bodies as a system and as a possible source that delivered water to Earth,” she said. “Add the large organic component in comets and you have two of the key ingredients for life.”

The findings help satisfy one of the major goals of the Deep Impact mission: Find out what is on the inside – and outside – of a comet.

To that end, NASA’s Jet Propulsion Laboratory teamed with the University of Maryland to slam a space probe into Tempel 1, then analyze materials from the comet’s surface and interior. On July 4, 2005, mission members hit their mark when the copper-tipped probe collided with Tempel 1 and created a spectacular extraterrestrial explosion 83 million miles from Earth.

Since then, the Deep Impact team has reported a few key findings. These include an abundance of organic matter in Tempel 1’s interior as well as its likely origins – the region of the solar system now occupied by Uranus and Neptune.

According to the new research in Science, the comet’s surface features three pockets of thin ice. The area the ice covers is small. The surface area of Tempel 1 is roughly 45 square miles or 1.2 billion square feet. The ice, however, covers roughly 300,000 square feet. And only 6 percent of that area consists of pure water ice. The rest is dust.

“It’s like a seven-acre skating rink of snowy dirt,” said Peter Schultz, professor of geological sciences at Brown, Deep Impact co-investigator and co-author on the Science paper.

Sunshine, Schultz and the rest of the team arrived at their findings by analyzing data captured by an infrared spectrometer, an optical instrument that uses light to determine the composition of matter.

Based on this spectral data, it appears that the surface ice used to be inside Tempel 1 but became exposed over time. The team reports that jets – occasional blasts of dust and vapor – may send this surface ice, as well as interior ice, to the coma, or tail, of Tempel 1.

“So we know we’re looking at a geologically active body whose surface is changing over time,” Schultz said. “Now we can begin to understand how and why these jets erupt.”

CALIPSO

The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite mission is pleased to announce an initial release of its data products. CALIPSO provides new insight into the role that clouds and atmospheric aerosols (airborne particles) play in regulating Earth's weather, climate, and air quality. CALIPSO is a joint mission between NASA and CNES, the French space agency.

CALIPSO's payload includes an active lidar (CALIOP), a passive Infrared Imaging Radiometer (IIR), and visible Wide Field Camera. This data release consists of data beginning in mid June 2006 and includes Level 1 radiances from each of the instruments. This release also includes the lidar Level 2 vertical feature mask and cloud and aerosol layer products.



On June 7, during its first day of lidar operations, CALIPSO observed the layers of clouds and aerosols shown here in an orbit over eastern Asia, Indonesia and Australia. In the lower right hand portion of the figure you can see the trace of the changing surface elevation of the Australian continent, a low horizontal line. Just above the surface, in a layer several kilometers deep, a layer of aerosol particles is shown in shades of orange and red. The greenish-yellow and blue colors indicate the lidar signal reflected from air molecules. Clouds are especially easy to detect and are displayed by the brighter colors of pink and white. We can see that some of these clouds are quite dense because the region below them is shown as nearly black -- the light from the lidar cannot penetrate the thick clouds. Also visible are thin tropical cirrus clouds shown in greenish-blue, at a height of 12 to 15 kilometers (about 7 to 9 miles). There was a range bias at the time this data was acquired, so the ocean surface appears to be at an altitude of -500 meters (-1650 feet).

This image also illustrates an exciting feature of the CALIPSO satellite, the ability to detect and track volcanic plumes. On May 20, 2006, a major lava dome collapse took place at the Soufriere Hills Volcano on the island of Montserrat in the Caribbean Sea. The dome collapse involved an explosion that sent ash clouds to 17 kilometers (about 10.5 miles) high, probably entering the lower stratosphere. The sulfur dioxide column from this volcanic activity has been tracked by the Ozone Monitoring Instrument (OMI) on NASA's Aura spacecraft for several weeks. On June 6 and 8, OMI observed the sulfur dioxide plume over Indonesia, and in the lidar curtain profile above you can see a thin scattering layer at an altitude of about 20 kilometers (about 12 miles). Because of the altitude and the correlation with the location of the plume, the very thin layer of clouds appears to be the aerosol component of the plume from Soufriere. The layer appears to be non-depolarizing, so it may be primarily composed of sulfuric acid droplets, rather than ash particles. Volcanic plumes such as this can be hazardous to air traffic if they cross air traffic lanes at the altitude where commercial aircraft fly. The ability of CALIPSO to observe the location, altitude, optical properties and movement of aerosols around the globe improves our ability to assess and forecast episodes of poor air quality.