You may not have seen it unless you were out very late last night, but the aurora did come around. It flared into a G2 moderate storm a few hours later than predicted. Looking back at the rhythmic expansion and contraction of the auroral oval, 3 a.m. CDT would have been the perfect to be out. All that was for naught at my house, where snowflakes fell from a starless sky. Hopefully, some of you were up late to catch the sky show. Tonight, a minor storm is forecast that will likely only be seen from the northern fringe of the U.S.
A new photo taken by NASA’s Cassini spacecraft provides us once again the opportunity to stop and consider how Earth fits into the big picture. Cassini snapped the image (actually a mosaic of images to create a single photo) of a pinpoint Earth shining through Saturn’s rings on April 12 at 12:41 a.m. when probe and planet were 870 million miles (1.4 billion km) away. Although far too small to see, the southern Atlantic Ocean faced toward Cassini during the shoot. If you look closely, you’ll spot a tinier, fainter pinprick of light immediately to the left of Earth ‐ the moon!
Saturn’s A ring is seen at top with the Keeler and Encke gaps visible across the middle and the F ring at bottom. During this observation Cassini was looking toward the backlit rings with the sun blocked by the disk of Saturn. Seen from Saturn, Earth and the other inner solar system planets are all close to the sun exactly the same way Mercury and Venus appear close to the sun as viewed from Earth.
Because Saturn is so much farther from the sun than the inner planets, they all appear to cluster very close to the sun from Cassini’s perspective. When this photo was taken, Earth was near its greatest apparent distance from the sun called maximum elongation from Saturn’s point of view, only about 5° or three fingers put together and held up at arm’s length against the sky. The only way to avoid the solar glare was for the spacecraft to block the sun using the ball of the planet the same way you’d hold up your hand to block the glare of the sun to take a picture of your own.
Opportunities to capture photos of the Earth from Saturn have been few and far between during Cassini’s 13-year-long stay at the ringed planet; the previous one included both planet and rings and was snapped on July 19, 2013. The flood of photos from the Cassini mission will soon end. At 10:46 p.m. CDT last night, Cassini entered the first of its Grand Finale orbits, a series of 22 weekly dives between the planet and the rings the spacecraft will perform before ending its mission on September 15. On that date, the probe will roar through Saturn’s upper atmosphere and burn up as a spectacular fireball, its remaining ashes sprinkled across white ammonia-ice clouds in silent ceremony.
Grand Finale — Cassini Mission. Nicely done mission summary with great visuals. Click here to watch it full-screen on youtube.
The first ring plane crossing is slated for midnight CDT April 25-26. Expect to see more amazing photos as Cassini draws ever closer to its final orbit. Space images possess the power to make us stop and consider where we’re at and who we are. This latest photo of Earth not only helps us better appreciate our blue home but how tolerance may ultimately preserve it.