Terra Cognita – Updated

See below for July 2015 update

When I first made this graphic, it included two unexplored worlds: Ceres and Pluto, and 2015 seemed impossibly far away.

Now here we are, and only one remains. Of course, all these places have centuries of exploration ahead, but the era of unveiling major worlds in our solar system for the first time is reaching its twilight, right before our eyes. I almost don’t want it to end.


Terra Cognita
Some worlds of the solar system before and after they were explored by recent spacecraft.

Updated July 2015

Now this chart is complete. (But the exploration of the solar system is not.)

before and after
Some worlds of the solar system before and after they were explored by recent spacecraft.

My Own Corner of Mars

On the 16th of February, at 3:16 pm (local Mars time), a robotic spacecraft orbiting the Red Planet trained its most powerful camera on the surface. It captured an image so detailed that if someone were standing there waving you could see their shadow.

This dune field inside a crater, on the floor of an ancient river bed, is one small part of that picture. Why did NASA engineers radio commands across 60 million miles of space in order to point the multi-million-dollar spacecraft at this particular spot?

Because I told them to. Continue reading “My Own Corner of Mars”

Maelstrom’s Edge!

Cassini has given us this new close-up of the outer edge of the bizarre and beautiful hexagon-shaped jet stream system at Saturn’s north pole, along with many smaller storms. Maybe ‘small’ isn’t quite the right the word. For a sense of scale: the entire Earth would fit inside the hexagon.

See more from the Cassini mission to Saturn.

Find out more about Saturn itself.

Saturn's polar hexagon,
A close-up of the outer edge of Saturn’s polar hexagon, along with many smaller storms, taken on March 28, 2014 and received on Earth March 31. NASA / JPL / SSI / animation by Bill Dunford

Dancing With Saturn

As I type this, the robotic spacecraft Cassini is traveling at 2.4 kilometers per second (about 5,300 MPH) relative to the planet Saturn. On April 9th, when Cassini makes its closest approach to the planet during this current orbit, the craft will reach nearly 9 kilometers per second (about 20,000 MPH). For all that amazing speed, the pictures we see from Cassini are usually still shots, arrestingly beautiful–but also arrested in time. Continue reading “Dancing With Saturn”


Harrison “Jack” Schmitt was the last person to step down onto the Moon. He was also the only professional geologist to work on the lunar surface, which he did during the Apollo 17 expedition to the Taurus-Littrow Valley.

The Moon’s geology still fascinates Dr. Schmitt. Just last week, in fact, he spoke about his lunar fieldwork to scientists gathered at the 45th Lunar and Planetary Science Conference being held this week in Texas. He told his audience that the samples and field notes from the Apollo 17 mission are still useful today, but that’s not all–there’s another, newer tool available to Moon explorers: the Lunar Reconnaissance Orbiter. High-resolution images from the robotic spacecraft provide fresh perspectives from on high, such as revealing boulder tracks at the Apollo landing sites that astronauts didn’t see from the ground.

Schmitt left the Moon in 1972. No one has been back since. But thanks to the Lunar Reconnaissance Orbiter, you don’t have to be an astronaut to see lunar landscapes up close. LRO returns images with such great detail that objects as small as individual boulders, or even human-made objects like the lunar landers, are easy to spot.

My favorite LRO shots are taken at a highly oblique angle rather than looking straight down. Views like that, especially when the sun is low on the horizon, almost look like what you might see if you were standing there in person.

At the bottom of this page I’ve gathered a few of these postcards from the Moon. Each offers a nice perspective on the landscape, but to really feel like you’re getting your boots dirty at the locations they show, you’ll want to click on the small pictures in order to zoom in on the details that are only visible in the much larger versions.

For example, here’s a detail from the Hausen Crater image:

Hausen Crater Central Peaks, Detail
Hausen Crater Central Peaks, Detail – Who’s up for a hike? The central peaks in the Moon’s Hausen Crater, a detail from the much larger image below. Credit: NASA / GSFC / ASU

And here’s another example, this one from Giordano Bruno Crater:

Giordano Bruno Crater, Detail

Giordano Bruno Crater, Detail – Beware of sliding boulders! A detail from a larger image of the Moon’s Giordano Bruno Crater, as imaged by LRO. Credit: NASA / GSFC / ASU

Here are some more lunar locations. Clicking on each will lead to a page where you can enlarge the image and explore the full desolation in all its magnificence. All of these images were captured in the past couple of years, and most have not been widely published elsewhere. Happy moonwalking!

Anaxagoras Crater
Anaxagoras Crater – An oblique view into the Moon’s Anaxagoras Crater, as seen by the Lunar Reconnaissance Orbiter with the Sun low on the horizon. Anaxagoras has a diameter of about 51 km. NASA / GSFC / ASU
Giordano Bruno Crater
Giordano Bruno Crater – A view of Giordano Bruno, a 22-km-wide impact crater on the far side of the Moon. When viewed large, the high resolution and oblique angle of this Lunar Reconnaissance Orbiter image almost make it seem like you’re standing right on the edge of the crater. Credit: NASA / GSFC / ASU
Antoniadi Crater Central Peak
Antoniadi Crater Central Peak – The unusually smooth floor of Antoniadi Crater includes the lowest point on the Moon. The Lunar Reconnaissance Orbiter captured this oblique view of the peak at the center of the crater, which is 143 km wide. NASA / GSFC / ASU
Posidonius Crater
Posidonius Crater, with its rille system named Rimae Posidonius. This oblique view of the 95-km-wide crater comes from the Lunar Reconnaissance Orbiter. NASA / GSFC / ASU
Hausen Crater Central Peaks
Hausen Crater Central Peaks – Hills at the center of Hausen Crater, as seen by the Lunar Reconnaissance Orbiter. The crater is nearly four kilometers deep. At high resolution, the angle and details visible in this image–right down to individual boulders–offer a moonwalker’s perspective. NASA / GSFC / ASU

This article originally appeared as a guest post on The Planetary Society site.