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Tag Archives: Solar System


A new interactive posting from National Geographic tells the story of the twin Voyager spacecraft, sent to explore the outer planets and the edge of our Solar System.

Links: The Voyager feature on the National Geographic website; a short movie.


An article in ScienceNews describes experiments on Earth about making a probe that can penetrate far enough into Europa’s surface ice to figure out what might be in Europa’s invisible ocean.

Credit: JPL-Caltech/NASA

Jupiter’s moon, Europa, looks just as desolate and uninviting as any other place in the outer Solar System. Its frozen façade is colder than the most frigid spot on Earth  by more than 100 degrees Celsius. Blasts of radiation sweep the surface. But beneath Europa’s inhospitable exterior, scientists think a vast ocean of liquid water flows. The moon’s seafloor might also bustle with activity from volcanoes and hydrothermal vents. If chemicals from the surface trickle down through the ice, as some scientists suspect, Europa could hold all the necessary ingredients for life.

Kevin Hand of NASA’s Jet Propulsion Laboratory in Pasadena, CA, says  “You’ve got incredible ecosystems of tube worms and crabs and fish and microbes [on Earth]. It’s anybody’s guess whether or not you’d find tube worms on Europa.”

The idea of exploring this vast ocean has launched a number of scientists on a quest for a space-ready ice drill. Somehow, such a device has to breach the moon’s icy shell — perhaps with blazing hot metal or the jagged teeth of a drill bit — and carry enough power for the job. The device has to be simpler and more reliable than anything used to bore through ice on Earth, and it will have to take care of itself — there’s no way to send a team of engineers to the far edges of the Solar System. And the entire ice-tunneling, power-toting, problem-free package needs to be light enough to launch beyond Earth’s gravitational grip. Research teams are now exploring the different approaches to penetrate, drill, burrow or melt through Europa’s icy shell.

Read more about these varied projects at ScienceNews.

Our Solar System seems like a neat and orderly place, with small, rocky worlds near the Sun and big, gaseous worlds farther out, all eight planets following orbital paths unchanged since they formed. However, the true history of the Solar System is far more riotous. Giant planets migrated in and out, tossing interplanetary flotsam and jetsam far and wide.

New clues to this tumultuous past come from the asteroid belt. Millions of asteroids circle the Sun between the orbits of Mars and Jupiter, in a region known as the main asteroid belt. Traditionally, they were viewed as the pieces of a failed planet that was prevented from forming by the influence of Jupiter’s powerful gravity. Their compositions seemed to vary methodically from drier to wetter, due to the drop in temperature as you move away from the Sun.


Credit: David A. Aguilar (CfA)

This traditional view has changed, as astronomers have recognized that the current residents of the main asteroid belt weren’t all there from the start. In the early history of the Solar System the giant planets ran amok, migrating inward and outward substantially. Jupiter may have moved as close to the Sun as Mars is now. In the process, it swept the asteroid belt nearly clean, leaving only a tenth of one percent of its original population. As the planets migrated, they stirred the contents of the Solar System. Objects from as close to the Sun as Mercury, and as far out as Neptune, all collected in the main asteroid belt.

Using data from the Sloan Digital Sky Survey, astronomers have examined the compositions of thousands of asteroids within the main belt. They found that the asteroid belt is more diverse than previously realized, especially when you look at the smaller asteroids. This finding has interesting implications for the history of Earth. Astronomers have theorized that long-ago asteroid impacts delivered much of the water now filling Earth’s oceans. If true, the stirring provided by migrating planets may have been essential to bringing those asteroids.

This raises the question of whether an Earth-like exoplanet would also require a rain of asteroids to bring water and make it habitable. If so, then Earth-like worlds might be rarer than we thought.  The paper describing these findings appears in the January 30, 2014 issue of Nature.

Links: Harvard-Smithsonian Center for Astrophysics press release; Nature article.

In this short article for The Conversation, Helen Maynard-Casely summarizes current efforts in exploring the Solar System, with missions underway to nearly every planet (and dwarf planet, Pluto).