Posted on by Nancy Atkinson

A Winged MESSENGER Flies By Mercury

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On January 14 the MESSENGER spacecraft skimmed just 200 kilometers (124 miles) above the surface of Mercury in the first of three flybys of the planet. Today (Jan. 15) the spacecraft will turn back towards the Earth to start down-linking the on-board stored science data it acquired during the flyby. The probe’s equipment gathered data on the mineral and chemical composition of Mercury’s surface, its magnetic field, its surface topography and its interactions with the solar wind. “This was fantastic,” said Michael Paul, a mission engineer. “We were closer to the surface of Mercury than the International Space Station is to the Earth.”

The closest approach was on the planet’s night side, the side facing away from the sun, and the spacecraft flew in the region along the equator. The scientific results will be available for the public at the end of January.

“The engineers and operators pulled off a tremendous feat, acquiring and locking onto the downlink signal from the spacecraft within seconds, providing the necessary Doppler measurements for the Radio Science team.” said MESSENGER Mission Systems Engineer Eric Finnegan, of the Applied Physics Lab in Laurel, Maryland. “The spacecraft is continuing to collect imagery and other scientific measurements from the planet as we now depart Mercury from the illuminated side, documenting for the first time the previously unseen surface of the planet.”

The signal from the spacecraft is tracked by the Deep Space Network, an international network of antennas that supports space missions.

In addition to Monday’s rendezvous, MESSENGER is scheduled to pass Mercury again this October and in September 2009, using the pull of the planet’s gravity to guide it into position to begin a planned yearlong orbit of the planet in March 2011. By the time the mission is completed, scientists also hope to get answers on why Mercury is so dense, as well as determine its geological history and the structure of its iron-rich core and other issues.

MESSENGER stands for Mercury Surface, Space Environment, Geochemistry and Ranging. Launched in 2004, it already has flown past Venus twice and Earth once on its way to Mercury.

Only one spacecraft has previously visited Mercury. Mariner 10 flew past the planet three times in 1974 and 1975, and mapped about 45 percent of its surface.

With Pluto now considered a dwarf planet, Mercury is the solar system’s smallest planet, with a diameter of 3,032 miles, about a third that of Earth.

A surface feature of great interest to scientists is the Caloris basin, an impact crater about 800 miles in diameter, one of the biggest such craters in our solar system. It likely was caused when an asteroid hit Mercury long ago. Scientists hope to learn about the subsurface of the planet from studying this crater.

True to its name, temperatures on the closest plant to the sun are quite “mercurial,” as Mercury experiences the largest swing in surface temperatures in our solar system. When its surface faces the sun, temperatures hit about 800 degrees Fahrenheit (425 Celsius), but when its faces away from the sun they can plummet to minus-300 Fahrenheit (minus-185 Celsius).

Original News Source: Reuters

Posted on by Nicholos Wethington

MESSENGER Flyby of Mercury January 14th

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If you thought you were good at pool, think again: in a game of interplanetary billiards, the MESSENGER team has guided its spacecraft to pass by Mercury for the first time on Monday, after a dizzying path that has already taken it past the Earth once and Venus twice.

The MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft will make its very first flyby of the planet on January 14th at 2:04 EST. It will pass within 200 kilometers (124 miles) of the surface. During the flyby it will be taking images and scientific measurements of the planet’s features.

The data it will be taking this time around will complement the measurements it will make when finally in orbit. MESSENGER will map the composition of Mercury’s surface, capture images at a resolution of hundreds of meters, and measure the structure of the planet’s magnetosphere and magnetic and gravitational fields.

Monday’s flyby will be the first time a spacecraft has visited Mercury in 33 years, since Mariner 10 did a series of flybys in the mid-1970s. During that mission, the spacecraft only imaged one hemisphere of the planet. MESSENGER will complete the picture, so to speak, by taking close-up images for the very first time of the other hemisphere.

The flyby will allow the spacecraft to map several features of Mercury that it will not be able to measure when in orbit, such as the magnetotail – the drawn out tail of the planet’s magnetosphere as it travels through space. It will also take over 1,200 images of the planet.

MESSENGER was launched in August of 2004, and has been making its way to Mercury by a number of different flybys of the Earth and Venus. The journey, though, is far from over. The spacecraft will make two more flybys of Mercury in October 2008 and September 2009, finally settling into orbit of the planet in March 2011.

It will then start a yearlong comprehensive study with its seven scientific instruments. When the journey is over, it will have traveled 4.9 billion miles (7.9 billion kilometers).

For more information and photos of the flyby, visit the official MESSENGER website.

Source: Johns Hopkins University Applied Physics Laboratory Press Release

Posted on by Fraser Cain

Podcast: Mercury

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We’re still digging through the thousands of comments and suggestions from the listener survey but we hear your requests and suggestions, and now you get to start reaping the benefits. Today we start our survey of the solar system with Mercury. What mysteries is it hiding from us? How similar is Mercury to the other rocky planets? How much do we really know about this first rock from the Sun?

Click here to download the episode

Mercury – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Posted on by Fraser Cain

MESSENGER’s Farewell Venus Video

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NASA’s MESSENGER spacecraft made its second and final flyby with the planet Venus on June 5th, 2007. It captured images and data on the way in, and it did the same as it sped away from the cloudy inner planet. The imaging team working with Messenger have stitched together the outbound images into a video, 50 frames long.

The images were captured using MESSENGER’s Wide Angle Camera. At the beginning of the sequence, the spacecraft was only 60,688 kilometers (37,710 miles) away from Venus, and at the end, it was 89,310 kilometers (55,495 miles) away. The first set of images were taken every 20 minutes, and then every 60 minutes at the end.

Click here to watch the video. Warning, it’s a 3 MB download, so this is only for the bandwidth unimpaired.

This is the end of MESSENGER’s visits to Venus, but that just means it’s time to get ready for the big show: Mercury. In January 2008, the spacecraft will make its first flyby of Mercury, and then two more on October 6th, 2008 and September 29th, 2009. It will make its final insertion maneuver on March 18, 2011.

Once it’s in a final mapping orbit, MESSENGER will begin analyzing Mercury with a suite of scientific instruments. These are designed to answer several key questions:

Why is Mercury so dense? Of all the inner planets, it’s the most dense by far. In fact, according to calculations, it would have to be 65% metal, twice as much as the Earth. One theory proposes that the planet became enriched with metal during its formation in the early solar nebula. Another possibility is that radiation from the Sun blasted away the outer rock layer of Mercury, leaving the iron rich core.

What is its geologic history? Only 45% of Mercury has ever been photographed by spacecraft. The part that was seen is heavily cratered and ancient, like the Earth’s moon. But there are younger plains between some of the older craters, and scientists think these could indicate volcanism in the planet’s history.

What is the structure of Mercury’s core? Scientists were surprised to discover that Mercury has a global magnetic field. This is a characteristic that it shares with the Earth. We know that the Earth has a liquid metal core, that acts as a natural dynamo. Does Mercury have one too?

What is the nature of Mercury’s magnetic field? Scientists are just beginning to understand the interactions between the Earth’s magnetic field, and the Sun’s solar wind. How does Mercury’s magnetic field differ from our own?

What are the unusual materials at Mercury’s poles? Mercury’s rotation is oriented so that its axis of rotation is nearly perpendicular to its angle of orbit. This means that in the polar regions, the sunlight hits the surface at a constant grazing angle. The interiors of some craters are in permanent shadow, and could have tiny deposits of water ice.

What’s the story with its atmosphere? You might be surprised to know, but Mercury has a thin atmosphere. It’s so thin that the gas particles don’t collide with each other. Instead, they bounce across Mercury’s surface; the official name for this is an exosphere.

So many questions. I can’t wait for MESSENGER to get to Mercury.

Original Source: MESSENGER News Release

Posted on by Fraser Cain

Flyby Images of Venus from MESSENGER

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NASA’s MESSENGER spacecraft made its second flyby of Venus earlier in June, and scientists have now released the images. The photographs attached to this story actually show the pictures the spacecraft captured as it was traveling away from Venus, on its way to an encounter with Mercury in the future.

MESSENGER has a suite of instruments designed to map out the details of Mercury’s surface; unfortunately, Venus is obscured by thick clouds, so it wasn’t able to see down to map out the terrain and minerals. That task will have to wait until it reaches Mercury. However, it did get an opportunity to observe the cloudy planet at the same time ESA’s Venus Express was observing. Scientists will be able to compare images, combine data, and calibrate scientific instruments from this double view.

The spacecraft has now past Venus for the last time; all of its future planetary encounters will be with Mercury. It will make three flybys of the closest planet to the Sun before going into orbit in 2011.

Original Source: NASA/JPL/JHUAPL News Release

Posted on by Fraser Cain

Mercury is Soft in the Middle

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A team of astronomers has discovered that tiny Mercury has a molten core, just like our own planet. The discovery was made using three ground-based radio observatories that bounced radio waves off the planet, and then analyzed the return signals.

Before this research, scientists were divided about the structure of Mercury. Most models predicted that it has an iron-rich core, but it wasn’t known if it had completely cooled, or was still liquid inside. Trace quantities of sulfur and other chemicals could have mixed in with the planet while it was forming, and this kept it from completely solidifying over time.

The astronomers first beamed a series of radio waves at the surface of Mercury, and then measured them as they bounced off the surface and returned to Earth. The returned signals were analyzed by a trio of radio telescopes: the Arecibo Observatory in Puerto Rico, NSF’s Robert C. Byrd Green Bank Telescope, and the NASA/JPL 70-meter antenna at Goldstone, California.

They were able to detect a wobbling of the signal that was double what you would expect from a planet with a solid core, but exactly the right amount for a planet with a liquid core.

Their research is the cover story of the May 4, 2007 edition of the Journal Science.

Original Source: NSF News Release

Posted on by Fraser Cain

Mercury’s Transit Captured by Hinode

The Japanese solar observing spacecraft Hinode captured this photograph of Mercury’s transit this week. Hinode, formerly known as Solar B, is currently in its shakedown period, where controllers ensure that each of its scientific instruments are working. But they couldn’t pass up this opportunity, so they pointed the spacecraft at the Sun, and watched the entire transit. Hinode should resume its normal science operations next month.
Continue reading “Mercury’s Transit Captured by Hinode”

Posted on by Fraser Cain

MESSENGER Flips Over to Get Some Shade

As NASA’s MESSENGER spacecraft gets closer to Mercury, it’s also flying closer to the Sun. And temperatures are rising. The spacecraft rotated 180-degrees on June 21, pointing its sunshade towards the Sun. This will keep temperatures to safe levels within the spacecraft. MESSENGER will keep this shade between itself and the Sun for the remainder of its mission. The spacecraft’s next big event will be its flyby with Venus on October 24.
Continue reading “MESSENGER Flips Over to Get Some Shade”