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MESSENGER Departing Earth

Leaving home: Image captured from the MESSENGER spacecraft during its flyby past earth in August 2005. Image credit: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Leaving home: Image captured from the MESSENGER spacecraft during its flyby past earth in August 2005. Image credit: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

MESSENGER has been in orbit around Mercury since March of 2011, but it began its journey seven years earlier, way back in August of 2004. Getting to the innermost planet takes quite a bit of work, involving a series of flybys past Earth, Venus, and eventually Mercury itself before settling into orbit.

The first of these flybys was past Earth in 2005, and MESSENGER snapped images over a 24-hour period as it was departing. The result is a movie that shows what it’s like to depart our home planet:

Is that amazing or what? As MESSENGER departs, Earth completes a full rotation. When the camera started rolling on August 2nd, the spacecraft was 40,761 miles (65,598 kilometers) above South America. By the time it took its last image one day later, MESSENGER was 270,847 miles (435,885 kilometers) away from Earth – farther than the Moon’s orbit!

This is what it looks like to leave our home. We should do this more often.

Hat tip to Mike Brotherton for the video link!

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Spring Equinox 2013 From Space

Yesterday, March 20 was the vernal equinox. That is, the moment in Earth’s orbit around the Sun where both hemispheres are equally lit. Not only did we get to experience an even 12 hours of daylight / 12 hours of night here on the surface, but it looked pretty cool in space as well:

GOES Satellite Captures Spring Equinox
Earth imaged by the GOES-13 satellite at 7:45 ET on March 20, 2013. Image credit: NOAA

As you can see, Earth is positioned with respect to the Sun in such a way that both the northern and southern hemispheres are equally lit. The image is a tad misleading as the straight line of the equator is oriented “directly” toward the Sun on the right, giving the impression that Earth’s axis is perpendicular to the plane of its orbit. But remember, Earth is tilted 23 1/2 degrees from the plane of its orbit, like this:

Axial Tilt of Earth. From Wikipedia
Axial Tilt of Earth. From Wikipedia

Putting all of this together and we have a representation of Earth in its orbit around the Sun, keeping its tilt in the same alignment year-round:

Earth's relative position to the Sun during its orbit. Not to scale, obviously. Source: Wikipedia
Earth’s relative position to the Sun during its orbit. Not to scale, obviously. Source: Wikipedia

So remember, Earth’s tilt is the reason for the season! Happy Spring!