Tag Archives: Neptune

Cassini’s Solar System Scrapbook

Cassini has completed its second-to-last ring plane crossing.  There’s only one more left before the final and fatal atmospheric entry.  But before it goes, Cassini completed a sort of family scrapbook of the solar system, by adding Neptune.  Here are some highlights of Cassini’s solar system scrapbook (which skips Mercury because it’s far too close to the Sun for Cassini to photograph):

Venus, Earth, and Mars

Venus, Earth and Mars, the only rocky planets easily observable from Saturn, as seen during the equivalent of a total solar eclipse around Saturn — Saturn is backlit by the Sun here. This was captured July 19, 2013.

Earth (and Moon), closeup from last image

This is a mega huge zoom in on the picture above.


Captured just before an Earth gravity assist maneuver, this is the Moon as seen on August 17, 1999. The spacecraft did not attempt to photograph the Earth during closest approach.

It’s worth also adding this. It’s the last image Cassini will ever take of Earth, captured April 12, 2017.


This was captured on December 29, 2000, while Cassini was grabbing a gravity assist boost from the giant planet.


There’s really no end of good Saturn pics, but I quite like this one, taken last year as Saturn approached the summer solstice in its northern hemisphere.


This blue planet against Saturn’s rings is not Earth. That little blue dot is the larger of the two “ice giants”, Uranus. I sincerely hope this is not the closest we’ll get to it in the 21st Century; it’s an astonishingly bizarre world that would seriously test a lot of basic science about planetary formation, magnetospheres, and so forth. This was captured April 11, 2014.


This is the most recent addition to the scrapbook, a zoom-in enhanced version of an image taken Aug. 10, 2017, commemorating Voyager 2’s flyby on August 25, 1989 and the 40th anniversary of the mission’s launch on August 20, 1977. This is Neptune and its largest moon, Triton.


Call it a consolation for not nabbing Mercury; Cassini captured this image of the dwarf planet Pluto on July 14, 2015, just as New Horizons was making its closest approach. (Naturally, New Horizons got much better pictures!)


It’s bittersweet, waiting for the end, but it helps to remember the amazing things Cassini has been doing.  Like Voyager 1 before it, Cassini is leaving behind portraits of our solar system.


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We’re going to Neptune, we’re going to Neptune….

Well, hopefully.  For the first time, NASA has made it more of a priority to put orbiters around the two remaining major planets, Uranus and Neptune, and is soliciting proposals for Uranus and Neptune orbiters, perhaps as a flagship-class mission that could be build as two copies, one for each planet, to launch sometime after 2020 or even 2030.  They’re also asking for proposals for cheaper options.  Even with this renewed focus, though, the missions face some stiff competition — from the as-yet-unplanned mission that will retrieve the samples collected by the 2020 Mars rover, from missions to study the oceans of Europa and Enceladus, and from a proposed Titan lander that already missed its opportunity in the last round (losing out to Mars InSight).  Plus, as outer-solar-system vehicles, they will certainly require plutonium, and that alone makes them expensive.

But I’m excited all the same!  This is a very long-range thing, so many of the scientists and engineers currently working at JPL will be retired before these probes reach their targets.  But with it finally a priority, perhaps these mysterious icy gas giants will finally get the missions they deserve.  Neither world has been visited since Voyager 2 made its solitary flybies of each world during the Grand Tour, and they remain deeply mysterious.

SpaceflightNow: Uranus, Neptune in NASA’s Sights for New Robotic Mission

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Something Old, Something New, Something Borrowed, Something . . .

. . . blue!

Blue, blue Neptune.  The close-up pictures we have of it are all old.  But NASA lets anyone freely borrow them for the sake of science, and in that people occasionally turn up something new, or at least something nobody else has spotted before.

A few years ago, Ted Stryk (an amateur, not a professional), stumbled upon something new in Voyager 2’s 1989 images of Neptune: the tiny moon Despina transiting the face of Neptune.  He composited these together into a beautiful single image showing Despina’s motion, and also its shadow across the most distant of the gas giants.

His composite image isn’t exactly new anymore, but APOD showcased it today, which got me thinking about the amazing new discoveries that can be made even from old data.  I wouldn’t be surprised if new discoveries are being made from Voyager data long after the probes have fallen silent sometime in the next decade.   It’s amazing, and it also serves as a reminder of how democratic this process really is.  Stryk didn’t do this with the resources of a university’s astronomy department, or a grant, or anything like that; he did it for fun.  😉  And if you are so moved, you can do it too!




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