Nasa has captured a stunning image of light reflection in the northern hemisphere of Titan, the largest moon of the planet Saturn, illustrating the presence of surface liquid on the planetary body.

The image, taken by the Cassini Spacecraft's visual and infrared mapping spectrometer on July 8, is the first of its kind.

Scientists had previously discovered lakes of surface liquid in the moon's southern hemisphere using infrared. It makes Titan the only other body besides Earth believed to harbour liquid on its surface.

Known as a specular reflection, the glint of light has been the focus of Cassini's mission since the craft made contact with Saturn in 2004. However, Titan's northern hemisphere has been shrouded in winter darkness for much of that time.

Titanic discovery: The glint, shown at the very top of the image, is captured for the first time

Sun only began to directly illuminate the northern lakes, which considerably outnumber the amount found in the southern hemisphere, during the moon's spring equinox in August this year.

'This one image communicates so much about Titan - thick atmosphere, surface lakes and an otherworldliness,' said Cassini project scientist Bob Pappalardo in a press release. 'It’s an unsettling combination of strangeness yet similarity to Earth.'

The glint comes from the southern shoreline of the sprawling Kraken Mare lake, which covers about 400,000 square kilometers of Titan’s surface.

Cassini team member, Ralf Jaumann, added: 'These results remind us how unique Titan is in the solar system. But they also show us that liquid has a universal power to shape geological surfaces in the same way, no matter what the liquid is.'

'Next, we want to find out more about Titan's liquid. Do we have some kind of weather there? Do we have changes with seasons? Does it rain? How does the liquid methane run across the surface?'

Scientists have been captivated by Titan for many years with the belief that its rich carbon atmosphere is similar to that found on our planet in its youth.

NASA's Hubble Space Telescope has discovered the smallest object ever seen in visible light in the Kuiper Belt, a vast ring of icy debris that is encircling the outer rim of the solar system just beyond Neptune.

The needle-in-a-haystack object found by Hubble is only 3,200 feet across and a whopping 4.2 billion miles away. The smallest Kuiper Belt Object (KBO) seen previously in reflected light is roughly 30 miles across, or 50 times larger.

This is the first observational evidence for a population of comet-sized bodies in the Kuiper Belt that are being ground down through collisions. The Kuiper Belt is therefore collisionally evolving, meaning that the region's icy content has been modified over the past 4.5 billion years.

The object detected by Hubble is so faint - at 35th magnitude -- it is 100 times dimmer than what the Hubble can see directly.

So then how did the space telescope uncover such a small body?

In a paper published in the December 17th issue of the journal Nature, Hilke Schlichting of the California Institute of Technology in Pasadena, Calif., and her collaborators are reporting that the telltale signature of the small vagabond was extracted from Hubble's pointing data, not by direct imaging.

Hubble has three optical instruments called Fine Guidance Sensors (FGS). The FGSs provide high-precision navigational information to the space observatory's attitude control systems by looking at select guide stars for pointing. The sensors exploit the wavelike nature of light to make precise measurement of the location of stars.

Schlichting and her co-investigators determined that the FGS instruments are so good that they can see the effects of a small object passing in front of a star. This would cause a brief occultation and diffraction signature in the FGS data as the light from the background guide star was bent around the intervening foreground KBO.

They selected 4.5 years of FGS observations for analysis. Hubble spent a total of 12,000 hours during this period looking along a strip of sky within 20 degrees of the solar system's ecliptic plane, where the majority of KBOs should dwell. The team analyzed the FGS observations of 50,000 guide stars in total.

Scouring the huge database, Schlichting and her team found a single 0.3-second-long occultation event. This was only possible because the FGS instruments sample changes in starlight 40 times a second. The duration of the occultation was short largely because of the Earth's orbital motion around the sun.

They assumed the KBO was in a circular orbit and inclined 14 degrees to the ecliptic. The KBO's distance was estimated from the duration of the occultation, and the amount of dimming was used to calculate the size of the object. "I was very thrilled to find this in the data," says Schlichting.

Hubble observations of nearby stars show that a number of them have Kuiper Belt-like disks of icy debris encircling them. These disks are the remnants of planetary formation. The prediction is that over billions of years the debris should collide, grinding the KBO-type objects down to ever smaller pieces that were not part of the original Kuiper Belt population.

The finding is a powerful illustration of the capability of archived Hubble data to produce important new discoveries. In an effort to uncover additional small KBOs, the team plans to analyze the remaining FGS data for nearly the full duration of Hubble operations since its launch in 1990.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute conducts Hubble science operations. The institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc. in Washington, and is an International Year of Astronomy 2009 program partner.

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Space shuttle Endeavour and its solid rocket boosters will be powered down and prepared for their move, or rollout, to Launch Pad 39A scheduled for early January 2010.

The six STS-130 mission astronauts will carry out a variety of administrative duties this morning at NASA's Johnson Space Center in Houston.

Commander George Zamka and Pilot Terry Virts also will practice shuttle landing techniques in T-38 jets and NASA's Shuttle Training Aircraft.

The first planets to be found around nearby stars have never been seen. Instead, astronomers have discovered them indirectly, inferring the existence of an unseen companion through its effects on the star itself.

So far, astronomers have only turned up huge planets that probably don't harbor life. However, future missions such as Terrestrial Planet Finder and its precursors will search for direct evidence of new planets as small as Earth.

The challenges of observing extrasolar planets stem from three basic facts:

• Planets don't produce any light of their own, except when young.
• They are an enormous distance from us.
• They are lost in the blinding glare of their parent stars.

For example, if there were a planet orbiting Proxima Centauri, the nearest star, it would be 7,000 times more distant than Pluto. Trying to observe this planet would be like standing in Boston and looking for a moth near a spotlight in San Diego.

The following is an overview of some of the planet detection methods that have thus far proved successful, as well as other methods currently in development.

Precise measurement of the velocity or change of position of stars tells us the extent of the star's movement induced by a planet's gravitational tug. From that information, scientists can deduce the planet's mass and orbit.

Why does a planet cause a star to sway? If a star has a single companion, both move in nearly circular orbits around their common center of mass. Even if one body is much smaller, the laws of physics dictate that both will orbit the center of the combined star and planet system. The center of mass is the point at which the two bodies balance each other.

The radial velocity method measures slight changes in a star's velocity as the star and the planet move about their common center of mass. In this case, however, the motion detected is toward the observer and away from the observer. Astronomers can detect these variances by analyzing the spectrum of starlight. In an effect known as Doppler shift, light waves from a star moving toward us are shifted toward the blue end of the spectrum. If the star is moving away, the light waves shift toward the red end of the spectrum.

This happens because the waves become compressed when the star is approaching the observer and spread out when the star is receding. The effect is similar to the change in pitch we hear in a train's whistle as it approaches and passes.

The larger the planet and the closer it is to the host star, the faster the star moves about the center of mass, causing a larger color shift in the spectrum of starlight. That's why many of the first planets discovered are Jupiter-class (300 times as massive as Earth), with orbits very close to their parent stars.

Astrometric displacement of the Sun due to Jupiter as at it would be observed from 10 parsecs, or about 33 light-years.

As with the radial velocity technique, this methods depends on the slight motion of the star caused by the orbiting planet. In this case, however, astronomers are searching for the tiny displacements of the stars on the sky.

The planets of our solar system have this effect on the Sun, producing a to-and-fro motion that could be detected by an observer positioned several light years away.

An important goal of the Space Interferometry Mission is to detect the presence of Earth-size planets orbiting nearby solar type stars via narrow angle astrometry. Similarly, the Keck Interferometry will conduct an astrometric survey of hundreds of stars to search for planets with masses as small as Uranus.

If a planet passes directly between a star and an observer's line of sight, it blocks out a tiny portion of the star's light, thus reducing its apparent brightness.

Sensitive instruments can detect this periodic dip in brightness. From the period and depth of the transits, the orbit and size of the planetary companions can be calculated. Smaller planets will produce a smaller effect, and vice-versa. A terrestrial planet in an Earth-like orbit, for example, would produce a minute dip in stellar brightness that would last just a few hours.

This method derives from one of the insights of Einstein's theory of general relativity: gravity bends space. We normally think of light as traveling in a straight line, but light rays become bent when passing through space that is warped by the presence of a massive object such as a star. This effect has been proven by observations of the Sun's gravitational effect on starlight.

When a planet happens to pass in front of a star along our line of sight, the planet's gravity will behave like a lens. This focuses the light rays and causes a temporary sharp increase in brightness and change of the apparent position of the star.

Astronomers can use the gravitational microlensing effect to find objects that emit no light or are otherwise undetectable.

Since planets do not give off their own light, observing them directly presents formidable challenges. Missions such as Terrestrial Planet Finder will rely on advanced technologies that can harness special properties of light to extend our vision. For a more detailed discussion of planet imaging, see Technology >Planet Imaging.

Still from animation portrays how the entire sky is flattened to the two-dimensional maps that IBEX presents. Credit: NASA/Goddard Space Flight Center
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NASA's Interstellar Boundary Explorer, or IBEX, spacecraft has made it possible for scientists to construct the first comprehensive sky map of our solar system and its location in the Milky Way galaxy. The new view will change the way researchers view and study the interaction between our galaxy and sun.

The sky map was produced with data that two detectors on the spacecraft collected during six months of observations. The detectors measured and counted particles scientists refer to as energetic neutral atoms.
› Press Release
› IBEX Briefing Visuals

NASA's Interstellar Boundary Explorer, or IBEX, spacecraft has made it possible for scientists to construct the first comprehensive sky map of our solar system and its location in the Milky Way galaxy. The new view will change the way researchers view and study the interaction between our galaxy and sun.

The sky map was produced with data that two detectors on the spacecraft collected during six months of observations. The detectors measured and counted particles scientists refer to as energetic neutral atoms.

The energetic neutral atoms are created in an area of our solar system known as the interstellar boundary region. This region is where charged particles from the sun, called the solar wind, flow outward far beyond the orbits of the planets and collide with material between stars. The energetic neutral atoms travel inward toward the sun from interstellar space at velocities ranging from 100,000 mph to more than 2.4 million mph. This interstellar boundary emits no light that can be collected by conventional telescopes.

The new map reveals the region that separates the nearest reaches of our galaxy, called the local interstellar medium, from our heliosphere -- a protective bubble that shields and protects our solar system from most of the dangerous cosmic radiation traveling through space.

"For the first time, we're sticking our heads out of the sun's atmosphere and beginning to really understand our place in the galaxy," said David J. McComas, IBEX principal investigator and assistant vice president of the Space Science and Engineering Division at Southwest Research Institute in San Antonio. "The IBEX results are truly remarkable, with a narrow ribbon of bright details or emissions not resembling any of the current theoretical models of this region."

NASA released the sky map image Oct. 15 in conjunction with publication of the findings in the journal Science. The IBEX data were complemented and extended by information collected using an imaging instrument sensor on NASA's Cassini spacecraft. Cassini has been observing Saturn, its moons and rings since the spacecraft entered the planet's orbit in 2004.

The IBEX sky maps also put observations from NASA's Voyager spacecraft into context. The twin Voyager spacecraft, launched in 1977, traveled to the outer solar system to explore Jupiter, Saturn, Uranus and Neptune. In 2007, Voyager 2 followed Voyager 1 into the interstellar boundary. Both spacecraft are now in the midst of this region where the energetic neutral atoms originate. However, the IBEX results show a ribbon of bright emissions undetected by the two Voyagers.

"The Voyagers are providing ground truth, but they're missing the most exciting region," said Eric Christian, the IBEX deputy mission scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "It's like having two weather stations that miss the big storm that runs between them."

The IBEX spacecraft was launched in October 2008. Its science objective was to discover the nature of the interactions between the solar wind and the interstellar medium at the edge of our solar system. The Southwest Research Institute developed and leads the mission with a team of national and international partners. The spacecraft is the latest in NASA's series of low-cost, rapidly developed Small Explorers Program. NASA's Goddard Space Flight Center manages the program for the agency's Science Mission Directorate at NASA Headquarters in Washington.

The Cassini-Huygens mission is a cooperative project of NASA and the European and Italian Space Agencies. NASA's Jet Propulsion Laboratory in Pasadena, Calif., provides overall management for Cassini and the Voyagers for the Science Mission Directorate.

Says: 'Build It and Infrared Surprises Will Come'

Artist's concept of Wide-field Infrared Survey Explorer. Image credit: NASA/JPL-Caltech
› Full image Engineers are rolling up their sleeves in preparation for building a telescope that will find the nearest star-like objects and the brightest galaxies. NASA has approved the start of construction on a new mission called the Wide-field Infrared Survey Explorer, which will scan the entire sky in infrared light.

"There's a whole infrared sky out there full of surprises," said Dr. Edward Wright, principal investigator for the mission at the University of California, Los Angeles. "By surveying the entire sky, we are bound to find new and unexpected objects."

An estimated $300-million mission, the Wide-field Infrared Survey Explorer, or "Wise," has been in the planning stages for the past eight years. It is scheduled to launch into an Earth orbit in late 2009. It will spend seven months collecting data.

Such extensive sky coverage means the mission will find and catalogue all sorts of celestial eccentrics. These may include brown dwarfs, or failed stars, that are closer to Earth than Proxima Centauri, the nearest star other than our sun. Brown dwarfs are balls of gas that begin life like stars but lack the mass to ignite their internal fires and light up like normal stars. They do, however, produce warm infrared glows that Wise will be able to see.

"Brown dwarfs are lurking all around us," said Dr. Peter Eisenhardt, project scientist for the mission at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We believe there are more brown dwarfs than stars in the nearby universe, but we haven't found many of them because they are too faint in visible light."

Wright, Eisenhardt and other scientists recently identified brown dwarfs using NASA's infrared Spitzer Space Telescope. Wise will vastly expand the search, uncovering those brown dwarfs closest to Earth that might make ideal targets for future planet-hunting missions. Recent Spitzer findings support the notion that planets might orbit brown dwarfs.

Wise might also find the most luminous galaxies in the universe, some so far away that their light has taken 11.5 billion years to reach Earth. Galaxies in the distant, or early, universe were much brighter than our own Milky Way galaxy, but dust thought to exist in these objects blocks much of their ultraviolet and visible light. These dusty coats light up at infrared wavelengths; however, the galaxies are few and far between, so they can be difficult to find. Wise will comb the whole sky in search of them.

"It's hard to find the most energetic galaxies if you don't know where to look," said Eisenhardt. "We're going to look everywhere."

The spacecraft's detectors will be approximately 500 times more sensitive than those of a previous infrared survey mission, called the Infrared Astronomical Satellite, a joint European-NASA venture that operated in 1983.

JPL manages the Wide-field Infrared Survey Explorer mission for NASA's Science Mission Directorate and Explorer Program. The Explorer Program is managed by NASA's Goddard Space Flight Center, Greenbelt, Md. The infrared cryogenic instrument for Wise will be designed and built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft will be built by Ball Aerospace and Technologies Corporation in Boulder, Colo. Mission operations will be conducted at JPL, and images will be processed and distributed at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. The Center for Science Education at the University of California, Berkeley, Space Sciences Laboratory, will manage the Wise education program. JPL is a division of the California Institute of Technology in Pasadena.

For more information on NASA's Wise mission, visit http://wise.ssl.berkeley.edu/ . For more information on NASA and agency programs, visit http://www.nasa.gov/home .

Media contact: Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.