Category: Asteroids

In August 2002, a bizarre looking asteroid made its closest approach to the Earth, skimming only 540,000 km above the Earth’s surface. That’s only 1.5 times the distance between the Earth and Moon. This gave astronomers an unprecedented opportunity to study the asteroid as it zipped past. Perhaps its most unusual feature? It’s shaped like a triangle.

Asteroid 2002 NY40 was first discovered as part of the automated LINEAR system in New Mexico on July 14, 2002. And then, just a month later it made this closest approach, coming within 540,000 km of the Earth. As it approached, it gained in brightness, reaching as high as 8th magnitude – not visible with the unaided eye, but easy to spot with binoculars or a backyard telescope (if you knew where to look).

2002 NY40’s close approach was a rare event. Near Earth asteroids only get this close once every 50 years or so. The last asteroid to get this near was NEA 2001 CU11 which passed just outside the Moon’s orbit on August 31, 1925. And it wasn’t discovered for 77 years after it made the flyby – astronomers had to go back and calculate when it passed us by.

On the evening of August 17/18, 2002 NY40 was scheduled to make its closest approach. During this night, astronomers around the world, including a team of researchers from Boeing and the US Air Force focused in on it. The Boeing/Air Force team brought the 3.6 metre AEOS Adaptive Optics telescope in Hawaii to bear and studied the asteroid in unprecedented detail, revealing a tremendous amount of surface features. With all this data, they were able to better understand the physical makeup of the asteroid, and get an idea of its structure. Their results will be published in an upcoming issue of the journal Icarus.

Oh yeah, and it looks like a triangle.

The first observations were made with the Raven telescope located at the Remote Maui Experiment site at the base of Haleakala in Kihei, Hawaii. The telescope was configured so that it could track a fast moving object, like 2002 NY40 as it moved quickly through the telescope’s field of view. The researchers modified their exposure times dynamically – ranging from 15 seconds to 60 seconds – as the asteroid came and went. This allowed them to get the same amount of light for every image; it let them compare apples to apples.

Getting these high resolution images of the asteroid was actually pretty difficult. At its very brightest, closest point, when Asteroid 2002 NY40 could be seen at the greatest resolution, it was moving very quickly across the sky – it covered the diameter of the Moon every 6 minutes, zipping across the sky at 65,000 km/hour. The background stars changed with every image. Instead of calibrating against a single set of background stars, the researchers had to calibrate each image against whatever images happened to be in the field of view at the time.

Asteroid 2002 NY40 is tumbling. Its main rotation takes about 20 hours, and its secondary rotation takes about 18.5 hours. Living on this asteroid would be disorienting, to say the least.

According to the best images, 2002 NY40 is about 800 metres across. Once again, this was challenging to discern because the asteroid was casting shadows on itself for part of the flyby. Only at the moment of its closest approach, were astronomers able to get a good image showing its size. This team’s estimates are actually much larger than previous estimates, which calculated it being 250-450 metres.

It turns out, astronomers were quite lucky with the flyby. 2002 NY40 was perfectly positioned during its closest approach to present its largest face to the Earth. With this much data, the researchers were able to classify it as a Q-type asteroid; an uncommon class of inner-belt asteroids that have some metal in them.

And of course, one of the most amazing observations is its strange triangular shape. Getting these images out of the raw data was the hardest part. Lewis Roberts, one of the researches that did the work remarked that, “the imaging was the most challenging. It was a difficult object to acquire good data on and the raw data did not look great. The image processing was top notch and pulled out some good images.”

Original Source: Arxiv Paper

It was a controversial theory when first proposed years ago, but now most paleontologists side with the theory that a large asteroid strike 65 million years ago delivered the killing blow that wiped the dinosaurs off the Earth. Astronomers have traced back what they think was its parent object, which struck another asteroid millions of years ago, creating many large fragments. Fragments that went on to devastate the Earth, and pummel the Moon.

The researchers include Dr. William Bottke and Dr. David Nesvorny from the Southwest Research Institute, and Dr. David Vokrouhlicky from the Charles University in the Prague. Their article, entitled An asteroid breakup 160 Myr ago as the probable source of the K/T impactor, is published in this week’s issue of the Journal Nature.

Asteroid 298 Baptistina was originally an asteroid 170 km in diameter, residing in the innermost region of the asteroid belt when it was struck by another asteroid 60 km across. This impact created the Baptistina family, and originally contained 300 objects larger than 10 km, and 140,000 objects larger than 1 km.

Over time, sunlight heated the asteroids caused them to slowly change orbits, drifting away from the original impact orbit. And this is how the scientists pieced everything together. They calculated how the orbits would change over time, and then traced the objects back until the were at the same point. This was 160 million years ago, before the Baptistina breakup.

Many of these objects were put into an orbit that would eventually intersect with the Earth. The team calculated that the rise in impacts over the last 100 to 150 million years was due to this collection. Fortunately we’re now at the tail end of it. Dr. William Bottke noted, “We are in the tail end of this shower now. Our simulations suggest that about 20 percent of the present-day, near-Earth asteroid population can be traced back to the Baptistina family.”

How does this connect to the dinosaurs? The asteroid that killed them was thought to have impacted 65 million years ago, carving out a chunk of the Yucatan peninsula. Fragments and sediments recovered from the impact site match the chemical composition of the Baptistina family. Researchers think there’s a 90% match between the two.

One of the most prominent craters on the Moon, Tycho, was probably created by one of these fragments as well. The 85 km crater was carved out 108 million years ago. Of course, nobody has actually measured the rocks in this region to know for sure. That’ll take a return visit of humans going to the Moon.

Original Source: SwRI News Release

Although NASA is gearing up to send humans back to the Moon, and eventually Mars, mission planners are also considering missions to Near Earth Objects (NEOs). These are the asteroids with orbits that cross our own, and might eventually impact the planet.

NASA completed a feasibility study to visit an asteroid in 2007, to see if its Constellation architecture would be compatible with a mission to an asteroid.

A digital animation company, DigitalSpace, has taken it upon themselves to animate a hypothetical mission to an asteroid, to demonstrate what it might look like. Keep in mind, this isn’t based on any official NASA material, it’s just a conceptual design created to stimulate discussion in the space community.

There are many benefits to visiting a near Earth object. Many have very similar orbits to the Earth, and so it would actually be surprisingly efficient for a spacecraft to journey to an asteroid – much less than to even go to the Moon. If scientists hope to predict the threat of NEOs, and develop a protective response, they need much more science. There’s nothing like human astronauts studying an asteroid from its surface, measuring it every way possible. Asteroids are also a source of easy resources. They have little gravity, so they’re easy to launch away from again.

There are numerous challenges for a mission like this as well. With the very low gravity, astronauts will need to be very careful when moving around. Asteroids can also spin quickly, making landing and takeoff hazardous.

If you want to see the potential mission, you can check out the video and animations here.

Original Source: DigitalSpace News Release