After only six months in orbit about Mercury, a NASA spacecraft has collected measurements that have discredited most theories about how our solar system’s innermost planet formed. Data gathered by instruments on MESSENGER reveal that Mercury’s surface has Earth-like levels of potassium and an even higher sulfur abundance, evidence that is at odds with most theories for how the super-dense planet came to be.
This image of Mercury was taken from MESSENGER in August 2011. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.
Launched in August 2004, MESSENGER stands for MErcury Surface, Space ENvironment, GEochemistry, and Ranging. It entered orbit about Mercury—the first spacecraft to do so—in March of this year.
Some of these new findings, published in a set of seven Science papers available online today, were first predicted in 2003 by Denton Ebel, curator in the Museum’s Department of Earth and Planetary Sciences, and Conel Alexander, a researcher in the Department of Terrestrial Magnetism at the Carnegie Institution of Washington. The two scientists recently published a separate paper highlighting their model in Planetary and Space Science.
“The composition of Mercury is very different from that of the Moon and other terrestrial planets,” said Ebel, who is a co-author on two of the new Science papers and the science lead for MESSENGER education and outreach efforts at the Museum.
The most striking difference between Mercury and other planets is the size of Mercury’s iron core, which makes up about 65 percent of the planet’s total mass. Earth’s core, by comparison, is just 32 percent of its mass. This characteristic is especially curious because the terrestrial planets—Mercury, Venus, Earth, and Mars—share similar early histories, each forming from accumulated dust, ice, and gas in the early solar nebula. Read more »
After flying nearly 5 billion miles over six years, the MESSENGER spacecraft is scheduled to begin orbiting the innermost planet. OnThursday, March 17, join Denton Ebel, associate curator in the Museum’s Department of Earth and Planetary Sciences, and Joe Boesenberg, senior scientific assistant in the department to watch a live feed from MESSENGER operations center at Johns Hopkins University and hear about new information that has been gleaned from the mission so far, such as the importance of understanding the planet’s high-density composition.
To date, three flybys of Mercury have yielded insights into this least explored terrestrial planet, starting with a historic flyby in January 2008. The Museum’s Science Bulletins chronicled the MESSENGER science team’s reaction as the orbiter’s first images of Mercury rolled in. Click below to watch the Science Bulletins video feature. For more about the MESSENGER mission, check out the article, “First Planet Finishes Last.”
Science Bulletins is a production of the National Center for Science Literacy, Education, and Technology (NCSLET), part of the Department of Education at the American Museum of Natural History.
When astrophysicists point their telescopes at the universe, iPhone and iPod touch users can now gaze with them using the Museum’s new app, Cosmic Discoveries. The app features nearly a thousand images of everything from the pockmarked surface of Mercury to the majestic Horsehead Nebula. Culled from the Museum’s archives and Science bulletins as well as dozens of space agencies and observatories around the world, the photos have been stitched together on the app’s opening screen to form a mosaic of the gas giant Saturn and its rings.
Users can pinch and zoom in on the mosaic to get a close-up look at images. Cosmic Discoveries also features in-depth stories about Comets, Galactic Clusters, Pulsars, X-Ray Galaxy Clusters, Protostars and Very Young Stars, Neutrino Bursts, Planetary Nebulae, and Planets in the Solar System. The stories chronicle how they were discovered, who discovered them, and other interesting facts.
Cosmic Discoveries was released to celebrate the 10th anniversary of the Museum’s Rose Center for Earth and Space and is available for free in the iTunes App Store.
Since NASA’s MESSENGER spacecraft was launched on a mission to study Mercury in 2004, it has returned stunning photographs of the innermost planet gathered during a series of flybys. (For a recent New York Times story about the surprising discoveries the spacecraft has already made, click here). Sean Solomon, principal investigator of MESSENGER, will be at the Museum on Monday, July 26, to speak about the new insights gleaned about Mercury’s high-density composition, its geological history, and its magnetic field in a special lecture. He will also discuss what’s next for MESSENGER, which is slated to enter Mercury’s orbit in March 2011. For some of the images retrieved from the mission so far, check out the gallery below.
Lift off from Cape Canaveral, Florida occurred in August, 2004, launching the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft on a 4.9-billion-mile journey to Mercury. The spacecraft, which was built for NASA by the Johns Hopkins University Applied Physics Laboratory, flew by Earth, Venus, and Mercury several times and will have circled the Sun 15 times before going into orbit around Mercury in March 2011. Credit: National Aeronautics and Space Administration or NASA
New research showing that that mercury levels are higher in some species of tuna could help consumers minimize their consumption of the silvery metal in their sushi and provide a powerful new tool for regulatory organizations. The new research—combining DNA barcoding at the Museum’s Sackler Institute for Comparative Genomics with analysis of mercury content at Rutgers University—is published in Biology Letters and shows surprisingly that tuna sushi purchased in supermarkets might be healthier than that from restaurants. The sushi made for supermarkets tends to be yellowfin tuna.
“We found that mercury levels are linked to specific species,” says Jacob Lowenstein, a graduate student affiliated with the Museum. “So far, the U.S. does not require restaurants and merchants to clarify what species they are selling or trading, but species names and clearer labeling would allow consumers to exercise greater control over the level of mercury they imbibe.”
Weighing a freshly caught yellowfin tuna enroute to Japan at Suisan fish market in Hilo, Hawaii. Credit: Joanna Burger
A plate of sushi with several pieces of tuna in the center (dark red is akami; light pink is toro). Credit: Joanna Burger
