A large comet spanning 3-5 km in width, large enough to have severe consequences if it had crash landed on Earth’s surface. Theorists hypothesized that it would be similar to the events that led to the extinction of dinosaurs 65 million years ago. These events may include unnatural drop in Earth’s atmospheric temperature, nuclear winters, and decreased sunlight.
http://en.wikipedia.org/wiki/Impact_event
A comet is made of rock, ice, dust, and organic compounds and can be several kilometers long in diameter. However, comets are fragile and can be broken into smaller pieces fairly easily. NASA noted that comet Elenin flew within 75 million kilometers of the sun and broke apart. As the comet approached Earth, it was only a cloud of debris, only visible through a telescope.
Don Yeomans of NASA’s Near-Earth Object Program says that the comet won’t be back for another 12,000 years. He noted that there has been hype on the internet about the comet and the consequences of it entering Earth. Yeomans said that in scientific reality, the comet is incredibly miniscule to have any impact on Earth’s gravitational pull to affect any environmental changes on Earth. The comet passed Earth at a distance that is ninety times the distance of the moon, and its mass was one-hundredths the size of the moon. If anything, the moon is currently exerting significantly more environmental changes than Elenin.
Image credit: NASA/JPL-Caltech
Maybe this event was nothing we should’ve been scared about in the first place. Only time will tell if the next space matter heading towards Earth is large enough for the hypothesized phenomena that were attributed to this comet.
The capability that living creatures have to repair themselves is astounding. Imagine you accidentally cut yourself with a knife while you’re making dinner. It’s not a huge deal, a little inconvientent perhaps, but nothing your body can’t handle. Now imagine cutting a sheet of plastic with that same knife. The plastic does not have the same capability to re-heal itself like we do. Once it’s cut, it can’t spontaneously heal itself back into it’s original conformation.
However, this is a phenomenon scientists have been trying achieve for nearly a decade. By experimenting with plastics, metals and carbon composites, researchers are attempting to create self-healing materials.
Mediocre Microcapsules
Self-healing fluid and hardening agent in a cracked material. Source: The University of Illinois
For the past decade, self-healing technology involves microcapsules filled with a self-healing fluid embedded into the material that is to be repaired, say a plastic. The fluid in the capsules is a monomer of the polymer plastic. Accompanying the microcapsules are catalyst hardening agents that react with the healing fluid to solidify it.
When the crack in the plastic punctures the microcapsules, the healing fluid within is released into the crack. The fluid polymerizes when it comes into contact with the catalyst, and the mixture seals the crack.
This method is effective, but not very efficient. It can repair cracks between fifty and one hundred micrometers wide, but the fluids have to move through the material by diffusion, which can take a long time. Also, there is a limit to the number of capsules that can be put in the material without weakening it’s structural integrity.
Circulatory Channels
Pressurized self-healing channels. Source: The Journal of the Royal Society Interface. Hamilton et al. September 2011.
New research being conducted by scientists at the University of Illinois attempts to mimic an animal circulatory system by copying the blood vessels and heart. Instead of having the self-healing fluids in capsules, they have put it in channels in the material. Similar to the microcapsules, when the channels are punctured, the fluid within them is released into the crack.
In addition to this change, pressure is also applied at the inlets and outlets of the channel to force the fluid into the crack in the material. This added pressure acts like a heart does in a circulatory system. The heart forces blood to move all throughout an animal’s body. The pressure applied to the self-healing fluid has the same effect. This technique ensures that the entire crack can be effectively repaired. With the applied pressure method cracks up to one millimetre wide can be repaired.
Current Applications
This technology has innumerable applications in infrastructure and engineering. NASA is looking into self-healing materials particularly for their space stations. Cracks and damages on these structures could risk the safety of the entire mission. With self-healing materials, the lives of astronauts are more secure, and they can focus on exploration, rather than restoration.
For more information on NASA’s work on self-healing materials, check out this video.
