NASA Spacecraft Snaps 1st Photo of Mercury from Orbit

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AP – This image provided by NASA is the first ever obtained from a spacecraft in orbit about the Solar System's …

SPACE.com Staff,
Space.com Space.com Staff,
space.com – Tue Mar 29, 5:45 pm ET

This story was updated at 5:32 p.m. ET.
The first spacecraft ever to circle Mercury has beamed home the first-ever photo taken of the small rocky planet from orbit, showing a stark landscape peppered with craters.
NASA's Messenger spacecraft snapped the new Mercury photo today (March 29) at 5:20 a.m. EDT (0920 GMT). The photo shows the stark gray landscape of southern Mercury, a view that is dominated by a huge impact crater. [See the first photo of Mercury from orbit]
"This image is the first ever obtained from a spacecraft in orbit about the solar system's innermost planet," Messenger mission scientists explained in a statement.
The new Mercury photo shows a region around the south pole of Mercury. A 53-mile (85-kilometer) wide crater called Debussy clearly stands out in the upper right of the image, with bright rays emanating from its center. [More photos of Mercury from Messenger]
A smaller crater called Matabei, which is 15 miles (24 km) wide and is known for its "unusual dark rays," is also visible in the image to the west of the Debussy crater, mission managers explained.
The new Mercury photo was posted to the Messenger mission website managed by the Johns Hopkins University Applied Physics Laboratory, which is overseeing the flight for NASA.
The photo is the first of 363 snapshots Messenger took during six hours of observations around Mercury. The images are expected to cover previously unseen areas of Mercury, terrain that was missed by Messenger during three previous flybys before it entered orbit.
Messenger arrived at Mercury on March 17, more than 6 1/2 years after its launch from Earth.
The spacecraft paused in its Mercury photo reconnaissance work just long enough to beam the new images back to Earth, mission managers said.
"The Messenger team is currently looking over the newly returned data, which are still continuing to come down," Messenger mission scientists said.
NASA plans to hold a teleconference with reporters on Wednesday to review the latest Mercury discoveries by the Messenger probe. The spacecraft's name is short for the bulky moniker MErcury Surface, Space ENvironment, GEochemistry, and Ranging.
The $446 million Messenger probe is expected to spend at least one Earth year studying Mercury from orbit. The spacecraft is in an extremely elliptical orbit that brings it within 124 miles (200 kilometers) of Mercury at the closest point and retreats to more than 9,300 miles (15,000 km) away at the farthest point.
The primary science mission phase will begin on April 4, when Messenger will start mapping the entire surface of Mercury, a process that is expected to require around 75,000 images. Scientists hope the spacecraft will help answer longstanding mysteries over the planet's geology, formation and history.
While Messenger is the first mission ever to orbit around Mercury, it is not the first spacecraft to visit the planet. NASA's Mariner 10 spacecraft flew by the planet three times in the mid-1970s.
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Up telescope! Search begins for giant new planet

Tyche may be bigger than Jupiter and orbit at the outer edge of the solar system

By Paul Rodgers

Sunday, 13 February 2011

If you grew up thinking there were nine planets and were shocked when Pluto was demoted five years ago, get ready for another surprise. There may be nine after all, and Jupiter may not be the largest.

The hunt is on for a gas giant up to four times the mass of Jupiter thought to be lurking in the outer Oort Cloud, the most remote region of the solar system. The orbit of Tyche (pronounced ty-kee), would be 15,000 times farther from the Sun than the Earth's, and 375 times farther than Pluto's, which is why it hasn't been seen so far.

But scientists now believe the proof of its existence has already been gathered by a Nasa space telescope, Wise, and is just waiting to be analysed. 

The first tranche of data is to be released in April, and astrophysicists John Matese and Daniel Whitmire from the University of Louisiana at Lafayette think it will reveal Tyche within two years. "If it does, John and I will be doing cartwheels," Professor Whitmire said. "And that's not easy at our age."

Once Tyche has been located, other telescopes could be pointed at it to confirm the discovery.

Whether it would become the new ninth planet would be decided by the International Astronomical Union (IAU). The main argument against is that Tyche probably formed around another star and was later captured by the Sun's gravitational field. The IAU may choose to create a whole new category for Tyche, Professor Matese said.

The IAU would also have the final say about the gas giant's name. To the Greeks, Tyche was the goddess responsible for the destiny of cities. Her name was provisionally chosen in reference to an earlier hypothesis, now largely abandoned, that the Sun might be part of a binary star system with a dim companion, tentatively called Nemesis, that was thought responsible for mass extinctions on Earth. In myth, Tyche was the good sister of Nemesis.

Tyche will almost certainly be made up mostly of hydrogen and helium and will probably have an atmosphere much like Jupiter's, with colourful spots and bands and clouds, Professor Whitmire said. "You'd also expect it to have moons. All the outer planets have them," he added.

What will make it stand out in the Wise data is its temperature, predicted to be around -73C, four or five times warmer than Pluto. "The heat is left over from its formation," Professor Whitmire said. "It takes an object this size a long time to cool off."

Most of the billions of objects in the Oort Cloud – a sphere one light year in radius stretching a quarter of the distance to Alpha Centauri, the brightest star in the southern constellation – are lumps of dirty ice at temperatures much closer to absolute zero (-273C).

A few of these are dislodged from their orbits by the galactic tide – the combined gravitational pull from the billions of stars towards the centre of the Milky Way – and start the long fall into the inner solar system.

As these long-period comets get closer to the Sun, some of the ice boils off, forming the characteristic tails that make them visible.

Professors Matese and Whitmire first proposed the existence of Tyche to explain why many of these long-period comets were coming from the wrong direction. In their latest paper, published in the February issue of Icarus, the international journal of solar system studies, they report that more than 20 per cent too many of the long-period comets observed since 1898 arrive from a band circling the sky at a higher angle than predicted by the galactic-tide theory.

No other proposal has been put forward to explain this anomaly since it was first suggested 12 years ago. But the Tyche hypothesis does have one flaw. Conventional theory holds that the gas giant should also dislodge comets from the inner Oort Cloud, but these have not been observed.

Professor Matese suggests this may be because these comets have already been tugged out of their orbits and, after several passes through the inner solar system, have faded to the point that they are much harder to detect.

So if it is real, Tyche may not only be disrupting the orbits of comets, it may also overturn an established scientific theory.

You can download a PDF showing the position of Tyche by clicking here