Big Impact: A Cosmic Collision
Heidi B. Hammel joined The Planetary Society's Board of Directors in 2005. A Senior Research Scientist with the Space Science Institute in Boulder, Colorado, Hammel herself lives in Ridgefield, Connecticut.
She received her undergraduate degree from the Massachusetts Institute of Technology in 1982 and her Ph.D. in physics and astronomy from the University of Hawaii in 1988. After a post-doctoral position at the Jet Propulsion Laboratory (Pasadena, California), Hammel returned to MIT, where she spent nearly nine years as a Principal Research Scientist in the Department of Earth, Atmospheric, and Planetary Sciences.
Hammel primarily studies outer planets and their satellites, with a focus on observational techniques. Hammel received the 2002 American Astronomical Society's Division for Planetary Sciences (AAS/DPS) Sagan Medal for outstanding communication by an active planetary scientist to the general public .
Question: What are scientists doing to protect us from cosmic collisions?
Heidi Hammel: From that comet crashing into Jupiter, we actually learned quite a bit about cosmic collisions. And you can put them in different categories. One of the first things we learned was these collisions happen on human lifetimes. This isn’t stuff that happened a billion years ago. This is going on right now, here in our solar system, massive collisions. And when I say massive, we took one of our impact sites that we had on Jupiter, and someone took it and mapped it onto a globe of the earth. Oh, it’s scary, you know. If one of these things hit the earth, we’re talking major disruption of the biosphere. We’re talking basically all of us dead. So, gosh, it’s a good thing it happened on Jupiter, not on earth. But at the same time, I mean, it was happening for real, and we could all see it. So it made the concept of cosmic collisions a very real concept on the large scale. Most people have already seen a cosmic collision. If you’ve seen a shooting star ever, you’ve seen a cosmic collision, because a shooting star is not a star. It’s a tiny dust or pea sized fragment of an asteroid or a comet hitting our atmosphere and burning up as it hits in, as it comes in. But those are tiny. It’s the big ones when they hit that could really do some serious damage to the planet and to the biosphere, the people and animals and plants and stuff living on the planet. So Shoemaker-Levy 9 made that real for us. We also learned quite a bit about the atmosphere of Jupiter. Now, you have to remember astronomy is almost always a passive science. Scientists normally like to do experiments. You know, they like to mix this with that and see what happens. They like to take this thing and poke it and see how it reacts. In astronomy we can’t do that. The stars, the planets, the galaxies, are so far away that we just look at them, and we have to learn things by looking at them. But in the case of Shoemaker-Levy 9, nature provided us with some ink that it injected into the atmosphere of Jupiter. The ink was the black material that the comet impacts created, which was basically burned up Jupiter atmosphere, we think. And that ink was dumped into the atmosphere, and then the winds of Jupiter could pick it up and throw it around and move it throughout the atmosphere. What a fantastic experiment for a planetary scientist. It’s like you couldn’t design a better experiment, you know. If I had this like giant pile of ink, inject it into an atmosphere, and watch what happened, you know, that’s what you’d want to do. And Shoemaker-Levy 9 did that. So it allowed us to trace out winds to see which direction they were blowing. Now we knew generally which way most of the winds were blowing in the cloud decks that we see, because we could watch a cloud, or we could watch what the cloud does. But in the upper atmosphere, these clouds are very, very thin and diffuse. And normally we can’t see them or trace them. But Shoemaker-Levy 9 injected chemicals into the upper atmosphere and using telescopes here on earth, we can trace the motion of those chemicals over a period of several years after the impacts, and watch the directions that the winds are blowing in the upper atmosphere. And they were moving more or less the direction that people predicted. The rates were not quite the same. And so that provides us with information we could use to better study the atmosphere of Jupiter itself. We couldn’t have done it without Shoemaker-Levy 9 impacts.
Question: What are scientists doing to protect us from collisions?
Heidi Hammel: Every year they have a conference about planetary protection, because the specter has now visibly been raised at these cosmic collisions actually could happen anytime. So there are scientists and engineers who are actively thinking about ways that we could either deflect an asteroid or comet, or remove the asteroid or comet in some way, move it out of its path. I mean, Hollywood has its own ideas about how to do that. We also have Bruce Willis saving the earth. But in point of fact scientists themselves have been thinking very seriously about how we might deflect an asteroid or comet. And one of the keys is finding them early, because if you find them early enough, and I mean like, 10, 20, 30 years before they’re going to hit the earth, you only need a tiny little push to get them to go off that orbit that they’re on and move them out of the way. It’s the ones that are coming in that you don’t find out about until three days before that, you know, that’s our worst nightmare, because there’s nothing really you can do about it in that case. We have actual programs and telescopes being built now that will have the capability of figuring out the whole population of these earth crossing asteroids. Right now we only know, we think we know about 10% that are out there, 10% of the population. That’s not a happy number, is it, because that means there’s 90% of the objects out there we don’t know about. With some of the large telescopes we’re developing today, we think that within a few, five, ten years of using there large telescopes to map out the whole sky a number of times, repeating, looking for moving objects, tracking their orbits, we think within 10 years we might be able to push that number up to 90%. So we really will have a much clearer understanding of what’s out there that might threaten us. Another big problem, of course, is understanding the bodies themselves. If it’s a comet that’s coming in versus an asteroid, and we think one is rockier and harder, and one is softer and fluffier, and you would want to treat them differently. I mean, you wouldn’t want to take a fluffy thing and then like blow it up, because then you got like a gazillion fluffy bits that are all more or less coming your way. Whereas a hard thing, you know, maybe you could set off like a nuclear bomb to push it off it’s track. So understanding what those space rocks or space ice balls, what they’re physically made of, that’s a big part of the MASA exp
As other planets have demonstrated, says Heidi Hammel, the threat is real. For Earth, an early warning system is critical.
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Water may be far more abundant on the lunar surface than previously thought.
- Scientists have long thought that water exists on the lunar surface, but it wasn't until 2018 that ice was first discovered on the moon.
- A study published Monday used NASA's Stratospheric Observatory for Infrared Astronomy to confirm the presence of molecular water..
- A second study suggests that shadowy regions on the lunar surface may also contain more ice than previously thought.
Credits: NASA/Daniel Rutter<p>Still, it's not as if the moon is dripping wet. The observations suggest that a cubic meter of the lunar surface (in the Clavius crater site, at least) contains water in concentrations of 100 to 412 parts per million. That's roughly equivalent to a 12-ounce bottle of water. In comparison, the same plot of land in the Sahara desert contains about 100 times more water.</p><p>But a second study suggests other parts of the lunar surface also contain water — and potentially lots of it. Also publishing their findings in <a href="https://www.nature.com/articles/s41550-020-1198-9#_blank" target="_blank">Nature Astronomy</a> on Monday, the researchers used the Lunar Reconnaissance Orbiter to study "cold traps" near the moon's polar regions. These areas of the lunar surface are permanently covered in shadows. In fact, about 0.15 percent of the lunar surface is permanently shadowed, and it's here that water could remain frozen for millions of years.</p><p>Some of these permanently shadowed regions are huge, extending more than a kilometer wide. But others span just 1 cm. These smaller "micro cold traps" are much more abundant than previously thought, and they're spread out across more regions of the lunar surface, according to the new research.</p>
Credit: dottedyeti via AdobeStock<p>Still, the second study didn't confirm that ice is embedded in micro cold traps. But if there is, it would mean that water would be much more accessible to astronauts, considering they wouldn't have to travel into deep, shadowy craters to extract water.</p><p>Greater accessibility to water would not only make it easier for astronauts to get drinking water, but could also enable them to generate rocket fuel and power.</p><p style="margin-left: 20px;">"Water is a valuable resource, for both scientific purposes and for use by our explorers," said Jacob Bleacher, chief exploration scientist in the advanced exploration systems division for NASA's Human Exploration and Operations Mission Directorate, in a statement. "If we can use the resources at the Moon, then we can carry less water and more equipment to help enable new scientific discoveries."</p>
A study finds 1.8 billion trees and shrubs in the Sahara desert.
- AI analysis of satellite images sees trees and shrubs where human eyes can't.
- At the western edge of the Sahara is more significant vegetation than previously suspected.
- Machine learning trained to recognize trees completed the detailed study in hours.
Why this matters<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU2MDQ1OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzOTkyODg5NX0.O3S2DRTyAxh-JZqxGKj9KkC6ndZAloEh4hKhpcyeFDQ/img.jpg?width=980" id="3770d" class="rm-shortcode" data-rm-shortcode-id="3c27b79d4c0600fb6ebb82e650cabec0" data-rm-shortcode-name="rebelmouse-image" />
Area in which trees were located
Credit: University of Copenhagen<p>As important as trees are in fighting climate change, scientists need to know what trees there are, and where, and the study's finding represents a significant addition to the global tree inventory.</p><p>The vegetation Brandt and his colleagues have identified is in the Western Sahara, a region of about 1.3 million square kilometers that includes the desert, <a href="https://en.wikipedia.org/wiki/Sahel" target="_blank">the Sahel</a>, and the <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/subhumid-zones" target="_blank" rel="noopener noreferrer">sub-humid zones</a> of West Africa.</p><p>These trees and shrubs have been left out of previous tabulations of carbon-processing worldwide forests. Says Brandt, "Trees outside of forested areas are usually not included in climate models, and we know very little about their carbon stocks. They are basically a white spot on maps and an unknown component in the global carbon cycle."</p><p>In addition to being valuable climate-change information, the research can help facilitate strategic development of the region in which the vegetation grows due to a greater understanding of local ecosystems.</p>
Trained for trees<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU2MDQ3MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNTk5NTI3NH0.fR-n1I2DHBIRPLvXv4g0PVM8ciZwSLWorBUUw2wc-Vk/img.jpg?width=980" id="e02c0" class="rm-shortcode" data-rm-shortcode-id="79955b13661dca8b6e19007935129af1" data-rm-shortcode-name="rebelmouse-image" />
Credit: Martin Brandt/University of Copenhagen<p>There's been an assumption that there's hardly enough vegetation outside of forested areas to be worth counting in areas such as this one. As a result the study represents the first time a significant number of trees — likely in the hundreds of millions when shrubs are subtracted from the overall figure — have been catalogued in the drylands region.</p><p>Members of the university's Department of Computer Science trained a machine-learning module to recognize trees by feeding it thousands of pictures of them. This training left the AI be capable of spotting trees in the tiny details of satellite images supplied by NASA. The task took the AI just hours — it would take a human years to perform an equivalent analysis.</p><p>"This technology has enormous potential when it comes to documenting changes on a global scale and ultimately, in contributing towards global climate goals," says co-author Christian Igel. "It is a motivation for us to develop this type of beneficial artificial intelligence."</p><p>"Indeed," says Brandt says, "I think it marks the beginning of a new scientific era."</p>
Looking ahead and beyond<p>The researchers hope to further refine their AI to provide a more detailed accounting of the trees it identifies in satellite photos.</p><p>The study's senior author, Rasmus Fensholt, says, "we are also interested in using satellites to determine tree species, as tree types are significant in relation to their value to local populations who use wood resources as part of their livelihoods. Trees and their fruit are consumed by both livestock and humans, and when preserved in the fields, trees have a positive effect on crop yields because they improve the balance of water and nutrients."</p><p>Ahead is an expansion of the team's tree hunt to a larger area of Africa, with the long-term goal being the creation of a more comprehensive and accurate global database of trees that grow beyond the boundaries of forests.</p>
Tea and coffee have known health benefits, but now we know they can work together.
Credit: NIKOLAY OSMACHKO from Pexels
- A new study finds drinking large amounts of coffee and tea lowers the risk of death in some adults by nearly two thirds.
- This is the first study to suggest the known benefits of these drinks are additive.
- The findings are great, but only directly apply to certain people.