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Mercury's Volcanoes

Mercury's Volcanoes Photo Credit: Science/AAAS

The planet Mercury seems placid compared to others in the solar system. But the MESSENGER spacecraft is revealing a more tumultuous past.


Transcript

Mercury’s ancient volcanoes. I’m Bob Hirshon and this is Science Update.

Compared to other rocky planets, Mercury is fairly quiet. No winds sculpt its surface, no flowing water carves channels, and no volcanoes spew lava. But according to planetary geologist James Head at Brown University, the planet was very different billions of years ago. Head is on the science team for MESSENGER, the spacecraft now in orbit around Mercury. In the journal Science, he reports the discovery of vast fields of ancient lava and volcanic vents.

Head:
These huge vents, measuring up to 25 km in length, appear to be the source of tremendous volumes of very hot lava that have rushed out, carving valleys and creating the teardrop-shaped ridges in the underlying terrain.

He says similar vents once existed in what is now the Northwestern United States, where the remains of huge lava flows from the Columbia River basin millions of years ago are still visible today. I’m Bob Hirshon, for AAAS, the science society.


Making Sense of the Research

NASA's MESSENGER spacecraft has been orbiting Mercury for about a year, sending us the most detailed images and data from the planet that humans have ever seen. As a result, long-held conceptions of Mercury's past and present have been challenged. 

In 1974, the spacecraft Mariner 10 sent the first closeup pictures of Mercury, and at the time, they revealed vast, smooth plains near the planet's north pole. Lava flows from volcanoes can create those kinds of smooth surfaces, as they have done on Earth and the moon. But the data from Mercury was inconclusive at the time. For example, the plains on Mercury were the same brightness as the planet's highlands, while on the moon, the volcanic deposits are significantly darker. More importantly, scientists back then weren't able to identify any actual volcanoes on Mercury.

Now, the MESSENGER mission has shed light on this decades-old mystery. Using its superior instruments, scientists have been able to study the fringes of Mercury's smooth plains, and the area beyond it. There, they found evidence of fissure vents—hugely long cracks in Mercury's surface from which lava could have flowed.

These lava flows would have been very different from both the dramatic eruptions on Earth, like the one that destroyed the ancient city of Pompeii, or the slow flow from the volcanoes of Hawaii. Instead, they would have flooded the surrounding area like a swollen river, drowning an area 60 percent as large as the continental United States. The team believes that much of the evidence for where this lava came from has been buried in the sheer volume of the eruption.

The new evidence shows that volcanoes played a major role in shaping Mercury, and there was probably similar activity on other parts of the planet. NASA researchers plan to use more data from MESSENGER to compare the chemical composition of these volcanic flood plains with that of the highlands, in order to better understand Mercury's interior and exterior composition.

Now try and answer these questions:

  1. What is the MESSENGER mission?
  2. Why was volcanism already suspected on Mercury?
  3. How did the MESSENGER data confirm that volcanoes shaped its surface?
  4. Why is it important to study the origin and composition of other planets?

You may want to check out the October 7, 2011, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: MERCURY SPECIAL REPORT–The MESSENGER spacecraft is revealing new discoveries about the planet closest to our sun.

The Science NetLinks tools Fact Challenge and Advanced Fast Fact Challenge test your knowledge of the solar system in general and Mercury in particular.

The tools Day on Mercury and Orbit & Rotation help you understand Mercury's orbit around the sun, and how it differs from Earth's.

NASA's official MESSENGER website has plenty of information about the mission, including multimedia displays, a timeline, and the latest news.


Going Further


For Educators

The Science NetLinks tools Fact Challenge and Advanced Fast Fact Challenge test students' knowledge of the solar system in general and Mercury in particular.

The tools Day on Mercury and Orbit & Rotation help students understand Mercury's orbit around the sun, and how it differs from Earth's.

NASA's official MESSENGER website has plenty of information about the mission, including multimedia displays, a timeline, and the latest news.


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