This image shows the moon, Earth’s only natural satellite, at center with the limb of Earth near the bottom transitioning into the orange-colored troposphere, the lowest and most dense portion of Earth’s atmosphere. The troposphere ends abruptly at the tropopause, which appears in the image as the sharp boundary between the orange- and blue-colored atmosphere. The silvery-blue noctilucent clouds extend far above Earth’s troposphere. Image credit: NASA

Earth’s atmosphere is critically important to all of us. In addition to providing us with air to breathe, it protects us from temperature extremes, harmful space radiation, and vast numbers of incoming meteoroids. The atmosphere is a very complex system that we are only beginning to understand. Gaining a better understanding of the atmosphere, how it protects us, and how we can protect it is in all of our interests.

In order to understand Earth’s atmosphere and how it works, it is essential to study atmospheres under a wide range of conditions beyond Earth. Examining atmospheres on other planets allows this. For example, by studying the atmosphere of Venus, we learned about the role of carbon dioxide as a greenhouse gas, and saw how it drives the temperature on Venus as high as 860 degrees Fahrenheit (460 degrees Celsius).

via NASA – Why LADEE Matters.

On the night of April 24 and the morning of April 25, 2013, the sun erupted with two coronal mass ejections (CMEs), solar phenomena that can send billions of tons of solar particles into space that can affect electronic systems in satellites. Experimental NASA research models show that the first CME began at 9:30 p.m. EDT on April 24. The second CME began at 5:24 a.m. EDT on April 25. Both left the sun traveling at about 500 miles per second and they are headed in the direction of planet Mercury.

via NASA – The Sun Sends Two CMEs Toward Mercury.

Image credit: NASA/JPL-Caltech › Larger view

A gauge on the Voyager home page, http://voyager.jpl.nasa.gov, tracks levels of two of the three key signs scientists believe will appear when the spacecraft leave our solar neighborhood and enter interstellar space.

When the three signs are verified, scientists will know that one of the Voyagers has hurtled beyond the magnetic bubble the sun blows around itself, which is known as the heliosphere.

The gauge indicates the level of fast-moving charged particles, mainly protons, originating from far outside the heliosphere, and the level of slower-moving charged particles, also mainly protons, from inside the heliosphere. If the level of outside particles jumps dramatically and the level of inside particles drops precipitously, and these two levels hold steady, that means one of the spacecraft is closing in on the edge of interstellar space. These data are updated every six hours.

Scientists then need only see a change in the direction of the magnetic field to confirm that the spacecraft has sailed beyond the breath of the solar wind and finally arrived into the vast cosmic ocean between stars. The direction of the magnetic field, however, requires periodic instrument calibrations and complicated analyses. These analyses typically take a few months to return after the charged particle data are received on Earth.

Voyager 1, the most distant human-made spacecraft, appears to have reached this last region before interstellar space, which scientists have called “the magnetic highway.” Inside particles are zooming out and outside particles are zooming in. However, Voyager 1 has not yet seen a change in the direction of the magnetic field, so the consensus among the Voyager team is that it has not yet left the heliosphere.

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