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Our Evolving Understanding of the Solar System: New Data, New Ideas


TNOs
The discovery of Eris (a Kuiper Belt object rivaling Pluto in size) -- and the anticipation of discovering many more such objects such as those depicted here -- resulted in the classification of Pluto within the new class of "dwarf planets." Credit: NASA/STScI

Robotic missions are exploring our solar system, and have been for almost fifty years. They assist us in a hunt for treasure -- of the wealth of information that they can gather about the conditions, formation and evolution of the solar system. Like most treasure hunters, we have some ideas of what we hope to find, but we often discover the unexpected -- providing a rich cache of new data that forces us to re-evaluate our ideas.

The Spitzer Space Telescope has detected
ingredients of pulverized comets around a
nearby young star-- evidence for a comet
storm akin to the hypothesized Late Heavy
Bombardment of our own solar system.
Comet Storm

Our understanding of the solar system is constantly changing as we make new discoveries. Nineteenth century astronomers found a variety of small asteroids, causing them to re-evaluate Ceres and re-classify it as an asteroid rather than a new planet. Similarly, the discovery of other large Kuiper Belt objects such as Eris and Sedna was shortly followed by the International Astronomical Union's new classification of distant, icy Pluto as a dwarf planet -- a change that remains controversial to this day.

Ongoing missions are making surprising discoveries throughout our solar system and beyond. The MESSENGER mission orbiting Mercury has found far more widespread volcanism than anticipated, and has confirmed the ground-based telescopic evidence that Mercury's core is still molten despite expectations that the planet would have completely cooled by now. The Dawn mission's investigation of the asteroid Vesta have revealed bizarre grooves and a massive impact basin. The fly-by missions EPOXI and Stardust-NExT discovered that different cometary nuclei can have very different characteristics. Missions studying distant stars and galaxies have also focused on objects within our solar system: the Hubble Space Telescope has made detailed observations of planets, comets and asteroids over the years and recently discovered a fourth moon around Pluto; and its sister telescope, the Spitzer infrared observatory, has studied distant planetary systems still cocooned in dust.

In addition to information to be returned from ongoing missions, data gathered from ground-based telescopes, past missions and return samples continue to provide new ideas. For example,

  • Astrobiologists examining life on Earth are finding a variety of microbes thriving in unexpected environments (check out Earth's Hidden Biospheres); these microbes have redefined our search for life beyond Earth. A new study has revealed that a group of ancient enzymes adapted to substantial changes in ocean temperature and acidity during the last four billion years -- evidence that life on early Earth evolved from an environment that was much hotter and more acidic than today's.
  • Discoveries of gas giants orbiting remarkably close to alien suns as a result of migration, along with asteroid data and issues with past models of the solar system's formation, have led to revolutionary models of planet formation. One such hypothesis, the "Nice model," suggests that the gas giants formed much closer to our sun and migrated out to their current positions through gravitational interactions -- scattering large populations of asteroids and comets and creating a Late Heavy Bombardment (pummeling the inner planets and moons with impactors around 3.9 billion years ago).

This topic explores the scientific process of gathering new data and formulating new ideas -- for more information about how data influences and changes scientific ideas, click to Background information. Check out Classrooms for activities. Find materials in Organizations and Clubs, and Educational Resources.

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Last Updated: 16 Apr 2014