Tag Archives: Space

ABC Asteroid XYZ


Spacecraft NEAR Shoemaker executed a soft landing on this asteroid, Eros, in 2000.

In “Asteroids Good and Bad” we touched on NASA’s plans to detect asteroids as well as to eventually land on one and “redirect” a piece of it into orbit around the Moon.

Why the interest in these space rocks?

Asteroids have pounded Earth for billions of years, and they’re not done with their mission, as the Chelyabinsk meteor rudely reminded us over Russia in 2013. With no warning it slammed into Earth’s atmosphere and exploded 28 miles up. Even that far away the relatively small 18-meter diameter asteroid fragment’s 500 kiloton equivalent explosion injured over 1,200 surprised people going about their business below it.

So what are asteroids? They consist of rocks and minerals, and come in three varieties: chondrite (C-class) made of clay and silicate rocks; stony (S-class) made of silicate and nickel-iron rocks; and metallic (M-class) consisting of mostly nickel-iron rock. They’re irregularly shaped, usually pitted or covered with craters.

Size matters, especially if one is headed our way. Most asteroids range from thirty feet to 330 miles in diameter, and none have any atmosphere. They orbit the Sun, rotating or tumbling along. More than half-a-million are known, but millions more are out there – exactly how many is unknown – and size matters.

Most asteroids orbit our Sun between Mars and Jupiter in the main asteroid belt. Between 1 and 2 million asteroids larger than 1 kilometer in diameter may exist in the main belt, yet most are still a million or more kilometers away from their nearest sibling. Just 150 have a companion moon, a few have two moons, and some asteroids occur as a pair of relatively equal-sized bodies. Astronomers have even spotted triple asteroids tumbling along together.

Although most asteroids may remain in the main belt, Jupiter’s massive gravity flings them out across the solar system from time to time. At present, 10,003 are known to approach Earth close enough to be considered potential collision hazards. These asteroids are called “Near-Earth Objects” or NEOs, and 861 NEOs have a diameter of 1 kilometer or more. Thus far scientists have tracked over 1,400 “Earth-crossers” that pose a significant threat. But as the surprise arrival of the asteroid over Chelyabinsk, Russia demonstrated, we’ve not yet located every potential collider.

How often do astronomers expect an asteroid to hit Earth? What evidence do we have that asteroids have hit Earth in the past? Where else can we find most asteroids other than in the main belt? How do asteroids get named, and did you know there’s an asteroid named for a cat called Dr. Spock? That’s weird.




Ceres, the largest asteroid, first discovered in 1801 by Giuseppe Piazzi, and visited by the Dawn spacecraft in February, 2015. Those bright spots remain a mystery, and Dawn continues taking pictures of Ceres from its closest approach, which continues the next few months. Image from NASA JPL via Dawn.

NASA’s new 2016 budget includes money for two asteroid missions. One of those missions continues an effort underway for years, the detection of near-Earth objects (NEOs), asteroids that pose a risk of colliding with our home planet. The other mission proposes to land on a near-earth asteroid, pick up a large boulder from its surface, and redirect the boulder into an orbit around the Moon. Once in a stable lunar orbit, manned missions would visit the asteroid fragment and retrieve pieces to return to Earth for detailed study.

Both missions complement each other and serve multiple roles. The detection mission will help protect Earth from a potentially cataclysmic collision with an asteroid. It’s happened many times in the past, and it continues to happen now. The biggest recent impact came in 2013 over Chelyabinsk, Russia, from an asteroid estimated at a mere 18 meters in diameter.

The detection mission would also help NASA find a nearby asteroid from which it might pluck a piece. That mission to “redirect” a piece of an asteroid into orbit around the Moon would build our understanding of what asteroids consist of and how they might contribute valuable minerals for industry. Perhaps even more important, the “redirect” mission involves landing on an asteroid and moving a piece of it onto a different trajectory, skills we would need if we ever detected an asteroid on a collision course with Earth and wanted to deflect it away.

How many asteroids are out there? How big are they? How many are on a course that might bring them into contact with Earth one day? What are they made of and does their composition mean we might benefit by capturing one and mining it? Could we deflect an asteroid on a collision course with Earth? What spacecraft missions have already studied asteroids, and what have we learned?

Stay tuned.


Plants in Space

Several weeks ago there was a big splash in the media about astronauts aboard the International Space Station (ISS) eating lettuce they had grown in Earth orbit. Having once spent ten weeks on a faculty fellowship at Kennedy Space Center working on potential problems associated with growing plants in space, I was curious about the progress that had been made since I had that experience.

Cosmonaut Maxim Suraev holds lettuce plants grown onboard the International Space Station.
Credits: NASA

Okay, I was more than a bit curious. I’m also writing a science fiction novel where plants grown in a greenhouse provide oxygen and food for the crew on a long-duration space mission. The reports from the ISS hardly dented the array of issues I’ve had to consider in creating a system that uses plants to provide crucial life-support for astronauts. By contrast, this recent story seemed almost trivial, a novelty. Astronauts had something better to eat for a change than vacuum-wrapped dry food or paste packaged months earlier back on Earth. I know NASA has grown plants in space for years. Is this the first time astronauts have officially eaten something they’ve grown in orbit? Really?

In fact, I have come up with a list of questions I hope to pose to NASA public relations contacts about plants in space. My questions follow below, and if anyone reading this list either has an answer, knows where I can find an answer, or knows who I might ask for an answer, please reply with a comment to this post.

1. Was the recent event on the ISS the first time space-grown plants have been eaten by astronauts in orbit?

I’ve found a tantalizing hint or two of other astronauts or cosmonauts eating space-grown food unofficially. But it seems that most space-grown plants were harvested and frozen or otherwise stored for shipment back to earth. Which leads to my next question.

2. Have space-grown plants ever been eaten by Earth-bound scientists before?

So if the space-grown veggies were promptly shipped back to Earth, did they get taste-tested there? I’ve gathered hints here and there about concerns that space-grown plants might not be safe for human consumption. I have to admit this sounds a bit like the worries about the safety of genetically-modified crops (GMCs). If it grows like a leaf of lettuce, is the same color – green, and looks like a lettuce leaf… Which leads to the next question.

3. Have toxic compounds ever been discovered in space-grown plants as a result of their growth in microgravity?

If it’s a serious concern, and not the wide-eyed speculations of someone who would rather bring food up to orbit from traditional farms back on good old planet Earth, then presumably space-grown plants have been tested for their safety. Has anything been found to justify further testing, or can our astronauts relax and enjoy any veggies they find the time and space to grow up there in the Space Station?

My last question, for now, goes back a bit further than the International Space Station and even the Space Shuttle. I think I know the official answer to this one, but it was a long boring ride (when nothing went wrong anyhow) from Earth orbit to the Moon.

4. Were plants ever grown by Apollo astronauts on a lunar landing mission either on the Moon or on the way there?

Once again, if you know part of an answer to any of these questions, please share. Even if you’re not sure, share your speculations. Or if you know where I might find an answer, or who I might ask, speak up. And thanks in advance.


It’s complicated, but that happens when you start messing around with time and space. Complexity, though, can make for an interesting plot, and that’s why I found this movie frustrating. The fabulous scientific accuracy with which Interstellar portrays travel across unfathomable distances and uncomfortable lengths of time is not matched by an equally sound scientific understanding of what might compel us to traverse the abyss between stars in the first place.

Opening video vignettes of mature citizens tell a tale of Earth’s decline. I could imagine each of them straight from Oklahoma or Texas during the Dust Bowl era. Earth’s climate has reduced the planet’s ability to supply food, and it’s only going to get worse. Dust storms threaten the health of the increasingly valuable as well as seemingly rare family farmer. Cooper (Matthew McConaughey) works hard and creatively to be a productive farmer, and passes that ethic on to his son. But the planet is in a downward spiral. And here’s my gripe. Climate change will undoubtedly affect our ability to grow food in the future. Our offspring will suffer hardships, some severe, if we allow climate change to proceed apace much longer. However, it is very difficult to imagine that the preferred solution will ever be emigration to another star system (whether the movie’s Plan A or B). As my wife is quick to point out, this is where “the willing suspension of disbelief” comes in. The basic plot makes sense only if you’re willing to ignore the fact that even travel to Saturn, much less through a nearly miraculous wormhole to another star system, would never be a viable solution to climate change on Earth. If you’re willing to overlook that little problem, and I highly recommend doing so, Interstellar is an entertaining and scientifically sound representation of what we know, or can reasonably guess, space travel, even between the stars, might be like.

Groundbreaking scientific visualizations inspired by the work of astrophysicist Kip Thorne (see The Science of Interstellar) lead the way. As an aside, Thorne has reported that the visualizations done for the movie actually led him to findings that he believes will support two new research papers in astrophysics. But before we get to the wormhole that enables interstellar travel, we have to reach Saturn. This is done with entertaining engineering acuity from the conventional rocket launch to the docking with an interplanetary ship designed to rotate to provide artificial gravity for the several-year trip out to Saturn.

Another bright spot for the film is the demography of its scientists. The leading bright light is Coop’s daughter, Murph. Chosen to lead humanity to its best future, Murph shines as a precocious young girl (Mackenzie Foy), an accomplished scientist (Jessica Chastain), and a family’s beloved matriarch (Ellen Burstyn). And she’s not alone, sharing the female science spotlight with Brand (Anne Hathaway), another daughter following in her father’s footsteps.

Of course, and unfortunately, it seems that few Hollywood endeavors touching science can leave out the mad scientist, and Interstellar is no exception. Dr. Mann (Matt Damon) plays the part here, and I’d prefer to believe he was also the author of the alternative scenarios presented to Coop and his fellow astronauts, the infamous Plan A and Plan B. Could the elder Dr. Brand (Michael Caine) have hatched this plot, perhaps. To avoid any more detailed spoilers, we’ll just leave it at that.

If you’ve read any other reviews, undoubtedly you know things get strange near the end, but time and space do get strange around the edges. But it is at the very end that Interstellar’s scientific credentials once again shine. When Cooper walks along the curving inside surface of a colony-ship, I was pleasantly reminded of physicist and space enthusiast Gerard O’Neill, who explained in the 1970s how cylindrical space colonies could become the off-planet future home of choice for humanity’s more adventurous. At the very least, consider solar power satellites in Earth orbit à la O’Neill’s vision in his book, The High Frontier. Built on-orbit or on the Moon with raw materials provided by asteroids or from the Moon itself, these space-based power stations could readily beam down to our home planet an ample supply of carbon-free energy that would allow us to avoid the worst scenarios of future climate change. It’s a solution one can imagine without a willing suspension of disbelief.