You wouldn’t think that books about astronomy and archaeology would have a lot in common, but Four Lost Cities (Annalee Newitz) and Under Alien Skies (Phil Plait) pack some odd similarities.

Both are about places we (mostly) can’t visit in person: Faraway planets in one case, the distant past in the other.

We have to piece together parts of the experience from what has come to us through time or through space: Telescopic observations, space probes, spectral analysis, and our understanding of physics — ruins, artifacts, aerial surveys and
what we know about people (both contemporary and in general).

For some sites we have very detailed and solid information: Angkor’s stone temples are still standing. Pompeii was well-preserved under volcanic ash and we still have first-hand writings about the city and its destruction. Mars and the moon have been extensively surveyed, including multiple landers and photographs from the surface. (And, in the case of the moon, a handful of people!)

Others require a lot of speculation: There’s a solid core of what we’ve figured out about Cahokia, but a lot of unknowns that we can sorta-kinda extrapolate from the histories and tales of surviving tribes in the area — but only to a point. Similarly, we know the rough structure of the TRAPPIST-1 solar system and some of its planets, but we have to speculate: if one of the planets in the habitable zone actually is habitable, what conditions would that require?

Both include major discoveries made within the last decade: Pluto and Charon were just a pair of dots until the New Horizons mission flew past it in 2015, bringing us pictures and measurements and so much data it took months just to download it from the probe back to Earth. Lidar surveys at Angkor in 2012 revealed the foundations of a vast metropolitan area around the temple complexes, upending our sense of how big the city was and identifying new sites to investigate.

It’s kind of funny how I read them so close together. Synchronicity and all that. They’re also both good (see also my review of Four Lost Cities and review of Under Alien Skies), and I’d definitely recommend them!

One of many cool facts brought up in Phil Plait’s new book, Under Alien Skies is that Martian sunsets are blue!

On Earth, nitrogen scatters light randomly, with bluer colors scattering more than redder colors, so the ambient sky is blue, but when you’re looking toward the sun at a shallow angle (like sunrise or sunset), most of the blue light is scattered into the next timezone and you see red and orange.

On Mars, tiny dust particles of iron oxides (rusty dust?) reflect yellow-orange light, making the daytime sky mostly a butterscotch color…but the particles that can stay aloft in the thin atmosphere are about the size of the wavelength of blue light, so they scatter blue light forward instead of randomly. So at the shallow angles of sunset and sunrise, the sky in the direction of the sun has more blue light than the yellows that are scattered in other directions.

Essentially the same process, but reversed because of the different content of the atmosphere!

Update: I’ve finished the book, and it’s well worth reading! Here’s a link to my review!

We attended Planetfest in Pasadena yesterday. It’s still going on now, a two-day event by the Planetary Society timed to match tonight’s landing of NASA’s Curiosity space probe on Mars.

Inflatable mockup of the Curiosity Mars rover.

I wasn’t really sure what to expect, but it was basically a bunch of space enthusiasts and people in the industry. SpaceX has a mock-up of their crew capsule, and other sponsors had exhibits with things like space plane mock-ups or geological drills. There was a life-size inflatable model of the Curiosity rover. There was a single track of programming with speakers on topics from the actual science of Martian exploration to the question of just why we explore space in the first place. Katie caught the Sally Ride tribute while I walked J around the exhibits, and we both watched Bill Nye’s talk about “Our Place in Space,” which he finished up with a fun science demonstration featuring liquid nitrogen marshmallows, gas toruses, a candle, and Robert Picardo.

SpaceX crew capsule mock-up.

The exhibits for “kids of all ages” turned out to be for kids from 4 on up. J wasn’t really interested in the Martian soil uplift demo, or the dirty snowball CO2 comet demo, but he liked watching the Xbox Mars Lander game, and he was fascinated by the robot that picked up and tossed basketballs. He had fun hanging out with grandma and grandpa, at least, and playing with a magnetic meteorite. (The tiny fragment of verified Martian meteorite was carefully mounted on a slab with plastic wrap to protect it from skin oils, but they had a couple of non-valuable rocks that you could pick up and hold.)

A robot that plays basketball.

A family friend invited us to the after party at the mall across the street. It was divided into two main areas: the sci-fi-themed dance floor out on the plaza, and a set of tables on the terrace above for the sit-and-talk crowd, where the main event was a participatory art project: A group had set up one blank postcard for each day of Curiosity’s journey from Earth to Mars, and was asking attendees to draw what they imagined the probe would write home about.

Planetfest party at Paseo Colorado in Pasadena

  • Irony: Someone just sent me email spam plugging the spam control features of their Twitter client. *headdesk*
  • Very cool! From @ThisIsTrue:

    COOL pic: Mars Orbiter gets photo of Mars rover, including tire tracks.

  • Kinda wanted to see Time Traveler’s Wife, but ad campaign & insistence that it’s not scifi are pushing me away. Low tomatometer not helping.
  • Note to self: No more light chocolate syrup. 50% less calories/carbs doesn’t help if you have to use twice as much to match the flavor.