‘Super Earths’ Around Nearby Stars Get New Attention

The features of planets referred to as “Super Earths” that orbit nearby stars are the subject of several presentations being given at the 225th meeting of the American Astronomical Society being held this week in Seattle. The results of new studies related to these Super Earths provide insights into exciting methods for determining the conditions on these planets, including the presence of oceans, that could lead to the finding of life outside of our solar system.

Super Earths are planets that exist in a distant star’s so-called “Goldilocks” zone, where the temperatures and conditions are “just right” for the development of life. Their masses are usually within the range of two to 10 times that of the Earth, and typically have larger diameters as well, leading to the Super Earth designation. These are expected to be rocky planets with molten cores, plate tectonics, and may have oceans. For example, a Super Earth called Gliese 581d, one of several planets orbiting a star designated Gliese 581, is looked at as one with a strong potential for having conditions that could support life. Gliese 581d is about eight times as massive as Earth, and is located in Gliese’s Goldilocks zone.

One of the meeting’s presentations examines whether the cycling of ocean between the surface and deeper in the earth’s mantle that happens on Earth could occur on Super Earths. There is more water in the Earth’s mantle than on the surface of the planet, due to the transport of ocean water into the planet’s interior by plate tectonics. Water in the mantle re-emerges at mid-ocean ridges and volcanoes. A proper balance in this process is necessary to maintain the presence of oceans for long time periods. The conclusion of this presentation was that more massive planets would provide even more stable conditions for maintaining the existence of oceans than Earth. The presence of oceans for millions or billions of years would encourage the development of life on Super Earths.

Another presentation discusses ways that the characteristics of the Earth can be used to detect Super Earths. This might be done by looking for the presence of clouds in the atmosphere, atmospheric chemistry, differences in surface color and textures, and even the presence of oceans as indicated by the reflection of light from the planet’s star off their surfaces.

Other papers presented at the meeting concerned combining Earth and space-based detection systems to better find planets orbiting other stars, and studying the differences in the reflection of light from the surface of turning planets, including Super Earths. A presentation on a means of analyzing the makeup of new planets and comparing it to known Super Earths is also on the schedule for the meeting.

Based on the subjects discussed at this meeting, it appears that scientists are in the process of finding new ways to characterize Super Earths and their oceans that have been identified so far and those that might be found in the future.