The Terra satellite is designed to study our planet from space, examining the environment over large scales and in high resolution. While passing over south Africa it took this seemingly normal — if still very beautiful — image:
I rotated it, so north is to the left. You can see land to the left, the southernmost tip of Africa, called Cape Agulhas. To the top is the Indian ocean, with the Atlantic to the right. A weather system is forming there, and all looks as it should… until your gaze settles all the way to the right (south). Wait… what’s the blue swirly thing?
Holy otology! Is that a giant ear?
Nope. It’s an eddy, a vortex, in the ocean, probably spun off the ocean current that flows around the southern cape of Africa. These eddies can dredge up material from deeper waters, including nutrients. Phytoplankton in the water feeds of those nutrients, and bang! Plankton bloom.
The plankton flows along with the water, coloring it blue, making it stand out eerily against the water. As I pointed out in an earlier post about these blooms, we can learn a lot about the environment from them. Plankton are sensitive to climate change, for example, and can act as indicators of the water’s physical characteristics.
When I see an image like this I think of all the funding cutbacks NASA is facing right now — and yeah, I’ll be writing about that soon. Our planet is on a cusp right now, and I can’t help but fret about the opportunities we might miss if we step back from space. Exploring space, even just being in space, has given us a perspective on our home world we couldn’t possibly have achieved otherwise. Some things, once begun, shouldn’t be stopped. Try as they might, some politicians can’t make us unsee what we’ve seen, and unlearn what we’ve learned.
Unless we let them, of course. I won’t, and I hope you won’t either. Let the picture above serve as a reminder: when it comes to keeping track of the Earth, we have to keep our eyes and ears open.
Last week, I posted an exceptional image of our home world as seen by the Suomi NPP Earth-observing satellite. The image was so popular that NASA released a second one, this time of the Eastern hemisphere, showing once again why it’s called the Blue Marble:
[Click to engaiaenate, or grab the terrestrialicious 11,500 x 11,500 pixel shot].
Like the other one, this is a mosaic, created over six different orbits — the bright north/south swaths are actually the reflection of the Sun in the ocean as the satellite passed over that area multiple times.
Although the satellite is in low Earth orbit, just a few hundred kilometers off the surface, the images have been mosaicked together to represent the view as if you were about 13,000 km (8000 miles) away. You’re seeing most of but not quite all of the entire hemisphere here. The inset image shows why; the farther you are from Earth the more of it you see.
If you’re having a hard time picturing that, imagine taking a camera and holding it a couple of centimeters from your floor. You only see a small section of the floor, right? Now take hundreds of pictures, moving the camera each time to get a different part of the floor. If you stitch those pictures together you have a complete image of your floor, even though it was too big to see from any individual shot. It’s as if you were hovering over the floor from higher up and took one shot.
That’s how this was done as well, though the pictures couldn’t just be stitched together; they had to be warped a bit to account for the Earth being round (near the Earth’s limb you’re seeing the ground at more of an angle than what’s directly below you). That’s why the image gives you such an overwhelming feeling of perspective, of actually being over the planet from all those thousands of kilometers away.
And I wonder… someday, our children may get this view every day, just by looking out a window. Every time I think about that, I get a chill. When I was a kid, that thought was science fiction. Now it’s maybe just a few more years down the road.
[UPDATE: Right after posting this, I got a feeling of deja-vu, and suddenly realized where I've seen this view of the Earth before: Apollo 17. What I wrote in that last paragraph is literally true: humans have seen this view before, and I hope that one day it will be routine to see it this way once again.]
Image credit: NASA/NOAA.