Astronomy events are few and far between these days as clubs cope with stay-at-home restrictions and institutional closures in response to the coronavirus pandemic. Most meetings and public star parties have been canceled for March and April while a few wait to see how events unfold.
McLaren gave a quick history of Mars exploration, from Mariner 4 which sent 21 photos back from Mars after a fly by in 1965 to the present work of Curiosity. He noted that Viking 1 in 1976 sent back the first photo from the surface of Mars. It was no accident that it shot its own foot.
“If we can only get one picture back, this is the most important picture, because they want to see how well the landing gear performed,” McLaren explained. “If they can see how the landing gear did, it gives them an idea of how they can improve the next lander.”
Unfortunately, experiments conducted by Viking were thought to rule out the possibility of life on Mars, though McLaren noted that there’s still some discussion about whether those experiments were conducted and interpreted properly. In any event, the zeal for Mars exploration cooled somewhat until the mid-1990s, when a Mars meteor discovered on Earth was found to contain what could be fossilized bacteria. This sparked new scientific interest in the Red Planet.
We returned to the surface of Mars in 1997 with Sojourner and Pathfinder, which proved we could land and drive around a rover on Mars.
“It truly was the Pathfinder that led us to design more sophisticated vehicles,” McLaren said. Spirit and Opportunity followed in 2004 and Curiosity landed in 2012.
Same car, new features
Perseverance, known as Mars 2020 until a recently concluded naming contest, will be something of a souped-up version of Curiosity. It’s based on the same design, but they’ve re-engineered the wheels, as those on Curiosity showed heavy wear unexpectedly early in its mission. Perseverance will also carry different instruments more specialized for astrobiology and geology. It will drill core samples and leave them cached on Mars awaiting a possible future return mission. And its cameras in general are more powerful and versatile than those of Curiosity. It’s mission is different, too. While Spirit and Opportunity were sent to follow the water and Curiosity is trying to figure out if Mars could have supported microbial life, Perseverance will actually be looking for evidence of that life.
A big challenge for the engineers will be delivering Perseverance to its landing site, which is in a crater called Jezero on the edge of what appears to have once been a lowland sea. There’s what looks like a former river delta on the edge of Jezero crater.
“The hope is that water was here for a long time, water flowed down here building this silt, that this is the most likely location where they hope to find any signs of life,” McLaren said.
A small target
The challenge is that the landing ellipse, the target they need to hit, is ten times smaller by area than that of Curiosity and some 300 times smaller than Pathfinder’s. They’ll used a technologically enhanced version of the sky crane technique that worked for Curiosity to try to hit that target.
The window for a possible launch opens on July 17 this year and McLaren said NASA expects to land Perseverance on Mars on February 18, 2021.
I was sorely tempted to headline this post “Alien megastructures discovered in Ballard,” but that would have meant sinking low into the sort of clickbait science that concerns Dr. James Davenport. Davenport, a research scientist at the University of Washington, gave a talk about the topic at the most recent gathering of Astronomy on Tap Seattle.
Davenport described himself as a big fan of science, and noted that to be such one needs to be OK with failure.
“Being wrong is just nature telling you, no, try again. Come up with a better idea, a better explanation for how the universe is working,” Davenport said. “If you love science, you have to love the struggle and you have to love truth.”
Davenport believes that it’s important to communicate about science, but often that leads to misconceptions or outright lies. Sometimes the misinformation is silly stuff, like trying to pump up the hype about a lunar eclipse by calling it the super blood wolf coyote Moon. Sometimes it’s just wrong. An example is what now seems like the annual return of social media posts announcing that Mars is going to appear as large as a full Moon in the night sky. This particular hoax may date back to 2003, when Mars actually was closer to Earth than it had been in some 60 thousand years. The falsehood was based on a nugget of truth, and Mars was an especially good target for astronomers that summer, but if you looked up it was still just a bright red dot in the sky. When someone doesn’t see that giant Mars they might conclude that science is stupid.
“Little by little we chip away at your interest, your excitement, your enthusiasm, your belief, and your trust in science as an institution,” Davenport lamented.
You’ve probably read many stories for which you found that the headline had little to do with the actual content. The purpose of the headline is to make you look. Davenport noted this phenomenon related to media coverage of Boyajian’s star, which brightens and dims in odd and unexpected ways. Scientists kicked around a lot of possible explanations for this observation. Maybe it’s a weird dust cloud or passing comets or debris from an asteroid collision. Someone even suggested a Dyson sphere or some other sort of “alien megastructure.” This grabbed the attention of the headline writers, and articles in Scientific American, the Washington Post, The Atlantic, Discover magazine, and others featured headlines about the possible discovery of alien megastructures, though the articles essentially said, “probably not.”
“There’s real science here but oh, golly, we need to be careful about reporting it,” Davenport said. “We have an obligation as scientists to be really careful and I worry that we’re not.” The truth about Boyajian’s star has yet to be figured out.
Where’s the rigor?
Another challenge for science communication is that there are some sites out there that are not exactly rigorous. For example, Davenport shared the following tweet from a site called Physics and Astronomy Zone.
You probably know that Pluto has not been reinstated. The tweet links to an old article—from April Fool’s Day. Also attached to that article are a slew of links to “stories” about the gifts men really want, amazing rebates for seniors, alien DNA in marijuana, and lots of other nonsense. It’s pure clickbait.
“This is a machine to get you to click on things, to get your eyeballs on things, to get you to engage with things so they make a few pennies,” Davenport said. “They do that a million times a day.”
There’s a lot of churn there. @zonephysics has more than 900 thousand Twitter followers.
“This is a huge impact for nonsense,” Davenport said. “Where is the celebration of truth?”
Davenport figures there are three things we can do to battle against the spread of pseudo-science and downright rubbish:
Communicate about science; don’t leave it to pseudoscientists spread misinformation
Share and intervene. Point out bunk when you see it.
Get the help of technology and tech companies to figure out how to weed out bad sources and find a way to remove the incentive for clickbait.
“We need other solutions besides just eyeball time equals dollars equals the only thing that matters on the Internet,” Davenport said. “We need tools that help us optimize for things beside just eyeball time. We need tools that help us figure out what’s the most efficient way to get knowledge across. What’s the most efficient way to help us identify bad actors who are spreading misinformation and intervening when people are trying to share that content.”
There’s some heavy lifting ahead.
“We need to do science outreach. We need help from everyone to spread truth and identify falsehoods. And we need the help of technology,” Davenport concluded. See below to watch his entire talk!
Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington. They’re taking a break in December and their next event will be held January 22, 2020.
The most recent gathering of Astronomy on Tap Seattle promised to take us inside the way science is really done, and delivered with tales of unexpected successes and a colossal fail that left a team of cosmologists with cosmic egg on their faces.
Leah Fulmer, a second year graduate student in astronomy at the University of Washington, gave a talk titled “Falling with Style: How Astronomy’s Most Intriguing Discoveries Happen by Accident.” Fulmer noted that astronomers have lots of choices when it comes to their research. They can select which part of the sky to examine, what to look at, how long to look, how often to look, and in which wavelengths of light to look, just to name a few. There’s lots of potential there.
“Every time we look at the universe in a new way we discover new phenomena that we never even expected to see,” she said. Fulmer shared three historical examples of such scientific serendipity.
The first was the detection of the cosmic microwave background (CMB) back in the 1960s. At the time it was theorized that 400,000 years after the Big Bang the CMB would have left its energy throughout the universe as a result of the event. Arno Penzias and Robert Wilson had access to a big radio telescope and were working on doing some radio astronomy. The problem was that they couldn’t tweak out some pervasive and persistent noise from their observations. Meanwhile down the road some theorists at Princeton were trying to figure out how to detect evidence of the CMB. Penzias and Wilson had already done it!
“By accident they took this telescope that NASA had built for satellite communicaiton, they stuck it out there, and they found literally the origins of the universe,” Fulmer said. “This changed our understanding of astronomy and physics as we know it and it was a really, really big deal, just by looking at something in a new wavelength.”
More recently the operators of the Hubble Space Telescope decided to pick out an empty, black part of the sky and have the scope stare at it for 100 hours. Many scientists thought this was a bit daft.
“They found what’s now known as the Hubble Deep Field,” Fulmer said. “They found an incredible plethora of galaxies that they never expected to see.” It revolutionized our understanding of the number of galaxies in the universe and added greatly to the types, shapes, and sizes of galaxies that we know about.
The Kepler Space Telescope found thousands of exoplanets, and collected data on so many things that scientists couldn’t possibly look at all of them. They enlisted citizen scientists through Zooniverse to help examine objects. Participants looked at the data and among their findings is an oddly behaving star for which its light curves defy explanation. We now know of it as “Tabby’s Star,” after astronomer Tabetha Boyajian, who wrote the paper about the discovery.
“To this day we don’t actually know what this star is,” Fulmer said. There have been lots of ideas about the odd light curves, from a random pack of asteroids that might be irregularly blocking light, some sort of cosmic catastrophe that kicked up debris, and even giant space structures built by an unknown civilization.
“It’s very precarious for an astronomer to suggest that this might be aliens,” Fulmer laughed, noting that the media would have a field day with that sort of thing.
The potential for discovering strange new things in the universe is about to increase. The Large Synoptic Survey Telescope is scheduled to go online in a few years, and when it does it will collect petabytes of data, doing a complete sweep of the sky every few nights for a decade.
Fulmer said a big part of her job in the project will be to help “develop an algorithm that is going to be able to systematically identify the things that we’ve never seen before.” That’s a tall order, combing all of that data for things we know about, things that have been theorized, and those that come out of the blue.
“We don’t what surprises we might find,” Fulmer said, “but that’s what makes it so exciting.”
Samantha Gilbert, a first-year graduate student in astronomy at the UW, told a story about a colossal and embarrassing failure. Her talk was titled, “Leaving the Competition in the Dust: A CMB Case Study.”
“The story I want to tell you tonight has everything: It has science. It has drama. It has egos. It has really esoteric vector math,” Gilbert said to laughter. “It encapsulates some of the things that are really wrong with how some people do science today.”
The story also involves the cosmic microwave background. Cosmologists are trying to figure out what happened between the Big Bang and the formation of the CMB 400,000 years later. A leading theory is that there was a period of inflation in the moments after the Big Bang during which the universe expanded rapidly. If that happened, it would have created gravitational waves, and those waves would have left behind a pattern in the CMB that we could recognize, called “B-mode polarization.”
“B-mode polarization is an extraordinarily difficult thing to detect,” Gilbert said, “but proving it exists, proving that inflation really happened by detecting the traces of inflationary gravitational waves” would be Nobel Prize-worthy.
That’s where the intrigue starts. One group striving for this discovery had an experiment called BICEP (Background Imaging of Cosmic Extragalactic Polarization), which was followed by BICEP2, which had more sensitive detectors than the first version and more of them. They found what they were looking for. In fact, the signal of B-mode polarization was even stronger than anticipated. The team declared the discovery during a 2014 news conference at Harvard, issued a video, broke out the bubbly, and in general whipped up lots of hoopla about the discovery.
In the following months some 250 papers were published in response to BICEP2. One of them was from BICEP’s main competitor, the Planck Experiment, and their point was that BICEP’s discovery was bunk and that what they detected was not B-mode polarization, but cosmic dust.
“The fact that BICEP2 had so confidently announced a result that was so quickly disproven had a rippling effect throughout the community,” Gilbert said. “Scientists were horrified because they thought, ‘now the public is going to discredit us, they’re not going to trust us.’ Journalists were also horrified because they felt they had a role in spreading disinformation.”
They were also seeing an ugly side of the scientific community.
The need for speed
How did this happen? BICEP principal investigator Brian Keating wrote a book about their process, titled Losing the Nobel Prize (W.W. Norton & Company, 2018). Gilbert summarized their decision-making.
She said BICEP2 only looked at one wavelength of light so they could get the results as quickly as possible. They knew about the possibility of cosmic dust, but didn’t have the tools to distinguish between dust and B-mode polarization. The Planck folks were thought to have the data, and BICEP asked them to share. They declined.
This led BICEP to jump to the conclusion that Planck also had evidence of B-mode polarization and were aiming to scoop them on the discovery and dash their dreams of a Nobel Prize. So they hurried to make the announcement. This might have worked out OK, if they’d been right, but the BICEP group made one other glaring error.
“They actually hadn’t put their paper through peer review,” Gilbert noted, generating groans among the science-savvy audience at Astronomy on Tap.
“That is a no-no,” she understated. “That is a bad thing to do because peer review is what makes science credible in the first place. It’s a really important check against the dissemination of junk science. You really need other scientists to independently assess your results.”
Gilbert said the bad decisions were all motivated by fear.
“Overly competitive environments are part and parcel of an individualistic conception of science and an individualistic conception of science says that the most important thing is to get a result before your competition,” she said. “When that’s the environment that you’re working in you tend to make decisions based on fear.”
“I would argue that the reason that BICEP2 made these decisions based on fear is that they were operating in such a toxically competitive environment that it became dysfunctional,” Gilbert said. “Whether you think competition is really good for science, really bad, or somewhere in between, I think that this case study shows us that it’s really worth thinking about the ways that we systemically and interpersonally encourage competition, and how that might jeopardize our ways of knowing.”
Gilbert said there’s hope for the future. The hunt for B-mode polarization continues, and BICEP and Planck are teaming up going forward, combining their resources and know-how in the work.
“Competition might be the most efficient way to A result, but collaboration is probably the most efficient way to a RELIABLE result,” she said.
Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington.
When we went on a road trip to a new place when I was a kid my dad would pick up a map from the nearest gas station. There were no gas stations on the way to the Moon, but the first astronauts to land there had a map anyway, thanks to the work of Harlan “Buzz” Reese and colleagues. His son, Tom Reese, talked about his father’s work at the most recent meeting of the Seattle Astronomical Society.
“What I’m honored to share tonight are images mainly from our dad’s collection, which for more than 50 years was pretty much just stuffed in boxes and cardboard tubes, but we now think of them as artifacts,” Tom Reese said. His father, who passed away in 2013, worked for many years at the Aeronautical Chart and Information Center (ACIC) in St. Louis. It was an office of the Air Force and was considered the premier mapping organization in the country. The elder Reese was a civilian who worked on the project creating charts of the Moon for NASA.
“They worked with the photographs from any source they could get, the best pictures that were available,” Reese said. That included images made by ground-based telescopes and lunar orbiters, and later photos shot by astronauts during Apollo missions. There was no image-editing software in the 1960s, but the folks at ACIC did have a cut-and-paste operation; they literally pieced together many of their charts by making copies of photographs, cutting them out, and building maps of larger areas as mosaics of many images. Some of them were huge, room-sized. They’d sometimes build these maps on the entire floor of a large room and walk around in stocking feet so as not to damage them too much. The charts include handwritten notes and tell-tale identification of the people who made them.
“My dad’s smeared fingerprints and careful mapping marks are also a down-to-Earth tribute to the other 400,000 human beings whose efforts made the journey possible,” Reese said.
Reese, an independent journalist, photographer, author, artist and teacher whose work as a newspaper and magazine photojournalist was nominated for Pulitzer Prizes during his career at The Seattle Times, spoke of a sense of awe and wonder when making a photograph of the Moon.
“I think it was with the same sense of wonder that my dad saved all these things that were actually scraps of his work,” Reese said, “but I also think he thought of these as a gift to be shared.”
Part of that wish came true this year, when several of the charts were included in the Destination Moon exhibit that wrapped up earlier this month at the Museum of Flight. Reese said he hopes the entire collection can some day wind up in a place where it can continue to tell a part of the story of the Apollo missions.
It’s amazing to think that the lunar orbiters that preceded Apollo were shooting photos using film, processing that film in space and then sending the images to Earth via radio. Today’s digital cameras on spacecraft capture far greater resolution. For the cartographers who mapped the Moon there was a good deal of art to go with the science.
“On the early maps of the Earth you can see where they would come to the limit of the known world and simply mark down ‘terra incognita’ or ‘beyond this point there be dragons,’” Reese said. “In the early mapping of the Moon precision was key, of course. But the audacity to fire three men packed into a rattling tin can to an unexplored world also required calculating on the unforeseen.” The mappers analyzed all of the data they had to give accurate representation of the sizes of and distances between lunar features so that the maps would be useful guides.
“Spacecraft with weapons in space are still pretty far in the future,” Dawson said. “We’re talking decades.”
Such a conflict would likely destroy every spacecraft in orbit, according to Dawson.
“That kind of a battle would end up disastrous for everyone involved,” she said. “The war would be over in a matter of minutes if that happend just outside of Earth orbit, and it would affect us on Earth for decades.”
That’s not necessarily what is preventing it from happening.
“Space is a very harsh theater of war,” Dawson said, listing the lack of air, extreme temperatures, radiation, and space junk as just the start of the problems such a war would face.
“Access [to space] is expensive and technologically challenging,” Dawson said. “It’s not like we would choose to go to outer space to engage in a war. It’s just that we have spacecraft up there that we all depend on, and so it is an area that is intriguing to countries that don’t agree with each other.”
The likely nature of war in space
War in space would be more subtle than a bunch of big explosions. A variety of weapons, including Earth-to-space, space-to-Earth, and space-to-space varieties are possible. Lasers, missiles, and various “kill vehicles” or “jammers” could be employed to foul up orbiting assets. Space debris itself could be a weapon. Take a look at this video from NASA:
Earth is at the center of the graphic, and each of the dots represent spacecraft, whether working or not. There’s a lot of junk out there. The Kessler syndrome is a scenario proposed in 70s by NASA scientist Donald Kessler; it posits that if there’s a dense enough amount of debris in space, then one collision or explosion could create a chain reaction of other colllisions or explosions.
“Pretty soon all you have is debris out there and you can’t get through it,” Dawson said. That would make it extremely difficult to operate existing satellites or launch new ones.
We sometimes don’t realize how much we depend on space systems. Wrecking all of those satellites would mess up a lot of things, from our GPS navigation systems to television signals, data exchange, air traffic control, communication systems, and weather forecasting. It would be a total pain.
Though a number of different entities are tracking space debris, it continues to get more challenging. Space X plans to launch 12,000 cube sats to create broadband service; these smaller objects are harder to track. There are unanswered questions about who owns space debris and who can or should clean it up.
“Major spacefaring nations have all been increasingly aggressive with military and surveillance operations in space,” Dawson added.
Preventing war in space
Dawson said the notion of preventing war in space is simple on its surface. It’s the same as preventing war on Earth. You use diplomacy, establish rules of conduct, and operate with openness and cooperation. She said we need more detail than is included in the 1967 Outer Space Treaty, a United Nations effort signed by more than 100 nations that set ground rules for peaceful exploration of space, and we need to figure out if and how existing international law applies to space. It’s all easier said than done.
“The international part of it is the difficult part,” Dawson said. The US has recognized its vulnerabilities in space and is working to protect its own assets, but other countries are doing their own thing.
“I try to be hopeful, but I think the international part of it is the biggest challenge,” Dawson said.
It takes a lot of detective work to figure out the nature of a type Ia supernova. Celestial Pig Pens and new tricks from old telescopes are contributing to the effort. That’s what we learned at the most recent meeting of Astronomy on Tap Seattle.
Messy Siblings: Supernovae in Binary Systems
Dr. Melissa Graham is a project science analyst for the Large Synoptic Survey Telescope, working out of the Astronomy Department at the University of Washington. Her main research focus is supernovae. In particular, she’s doing a lot of work on type Ia supernovae, which occur in binary star systems. One of the stars involved will be a carbon-oxygen white dwarf star.
“It’s a star that wasn’t massive enough to fuse anything else inside the carbon layers,” Graham explained. Outer layers of hydrogen and helium are thrown off in a planetary nebula phase, so the carbon and oxygen are what’s left.
“Carbon-oxygen white dwarf stars are very compact, very dense, about the size of the Earth but they can be up to about 1.4 times the mass of the Sun,” Graham said. These stars are pretty stable as stars go, so they don’t blow up under normal circumstances.
“When we do see these kind of supernovae that are clearly the explosion of carbon-oxygen white dwarf stars we have to wonder why,” she said. It turns out there are two possible scenarios. The binary can be a pair of carbon-oxygen white dwarf stars that spiral in on each other, merge, and then explode. Or the binary can include one white dwarf and a more typical hydrogen-rich companion star.
“In this case the companion star can feed material onto this carbon-oxygen white dwarf star, might make it go over 1.4 solar masses, become unstable, and then explode,” Graham said.
Which is which?
The key to figuring out which of these scenarios actually occurred is to take a look at the area around the supernova. If the companion is a more hydrogen-rich companion star, the neighborhood can get a little messy.
“It’s sort of like a celestial Pig Pen star that leaves a lot of material lying around,” Graham said. A blast from a supernova can interact with this material and cause it to brighten. The trouble is that astronomers typically only observe type Ia supernovae for a couple of months; they fade quickly. So if this extra material is far away from the event, they might not see the interaction. The answer is patience, to look at the supernova sites for up to 2-3 years after.
Graham did exactly that, using the Hubble Space Telescope to keep an eye on the locations of 65 type Ia supernovae.
“Out of these 65, I very luckily found one” in which there was brightening much later. They checked the spectrum of the light and found hydrogen, a sure sign that the companion in this particular type Ia supernova was a Pig Pen. Graham suspects that up to five percent of such explosions involve messy sibling stars.
“This marks a massive increase in our ability to both find and characterize supernovae,” she said.
Old scope, new tricks
While we wait for LSST an old workhorse telescope is doing interesting work in a similar vein. Professor Eric Bellm of the UW works with the Zwicky Transient Facility (ZTF), which uses the 48-inch telescope at Palomar observatory in California. The scope is a Schmidt, completed in 1948, and for years it was the largest Schmidt telescope in the world. It’s main function at first was to use its wide-field view of the sky to create maps that helped astronomers point Palomar Mountain’s 200-inch Hale Telescope.
The 48-inch was used to do numerous sky surveys over the years. It discovered many asteroids, and Mike Brown used it to find the dwarf planets he used to kill Pluto. The old photographic plates gave way to modern CCDs, and Bellm became the project scientist for the Zwicky Transient Facility—named for astronomer Fritz Zwicky, a prolific discoverer of supernovae—in 2011.
They outfitted the scope with a new camera with 16 CCDs that are four inches per side. They got some big filters for it and put in a robotic arm that could change the filters without getting in the way of the camera. They started surveying in March of last year and can photograph much of the sky on any given night.
“That’s letting us look for things that are rare, things that are changing quickly, things that are unusual,” Bellm said.
Examples of what the ZTF has found include a pair of white dwarfs that are spinning rapidly around each other, with a period of just seven minutes. They can see the orbits decay because of gravitational wave radiation. It has discovered more than 100 young type 1a supernovae. And it found an asteroid with the shortest “year” of any yet discovered; its orbit is entirely within that of Venus.
It’s doing the same sort of work that the LSST will do when it comes online.
“It’s super cool that we’ve got this more than 70 year old telescope that we’re doing cutting-edge science with thanks to the advances of technology,” Bellm said.
Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington, and typically meets on the fourth Wednesday of each month at Peddler Brewing Company in Ballard. The next event is set for September 25.
As we look back at the 50th anniversary of the Apollo 11 Moon landing, Toby Smith notes that the most interesting science that came out of the mission was a bit of a surprise. Smith, a senior lecturer in astronomy at the University of Washington, gave a talk at the most recent meeting of Astronomy on Tap Seattle.
“There’s only one reason Apollo existed—to beat the Soviet Union to the surface of the Moon,” Smith noted. Few considered the mission to be scientific. “It wasn’t fully embraced by the scientific community even in its day, even among planetary scientists.”
But they figured as long as they were there, they should do some sort of science.
“This little bit of science they did fundamentally changed how we view not only the Moon, but the Earth-Moon system and our solar system,” Smith said.
The Apollo 11 landing site, the Sea of Tranquility on the Moon, is essentially an ancient lava flow, a featureless plain of cooled volcanic rock, Smith said. Think of it like Big Island of Hawaii, except you don’t really see the solidified lava on the Moon. The surface is soft, ground down and rounded off into a soft powder by billions of years of impacts. As Neil Armstrong observed just after his first step, it has the consistency of flour. That consistency almost accidentally led to the mission’s best science.
Armstrong spent about 15 minutes of the two-and-a-half hour Moon walk picking up rocks and putting them into a box. At the end he collected nine scoops of lunar regolith and dumped it into the Apollo Lunar Sample Return Container (a fancy NASA term for the case for rocks) as sort of a packing material so the larger rocks wouldn’t clatter around. If they’d taken any styrofoam peanuts he might have used those instead.
Naturally, when this material was brought back to Earth, the scientists looked at it, and Smith said it just might be the most studied geological sample ever.
Smith noted that the regolith is highly angular; lunar dust is sharp.
“This is not material that was broken up by being tumbled,” he said. “This is material that was broken up by being fractured by impacts.”
It’s a diverse sample. It contains basalt, breccia (material created by impacts that shatters and sometimes melts back together), and impact spheres. There was also one unusual, bright white material in the collection. It turned out to be anorthosite, which makes up about four percent of the sample.
“It represents a piece of the original crust of the Moon long since destroyed by four and a half billion years of impacts,” Smith explained. Anorthosite is an igneous rock, like basalt, that comes from the cooling of melted rock. Basalt is created when lava moves across the ground, but Smith noted that anorthosite doesn’t work that way.
“Anorthosite forms in big pools of lava, huge pools of lava, huge chambers of lava,” he said. “As these chambers of lava slowly cool over time, the anorthosite floats to the top.”
“If this was found on the Moon it must mean that at some point early in the Moon’s history it must have been almost completely molten,” Smith added. This information made scientists re-think their notions about the origins of the Moon.
“Before Apollo there was no indication that the whole, entire Moon was almost completely melted,” he said.
The leading theory about the formation of the Moon these days is that something pretty big, about the size of Mars, smacked into the early Earth, and that material flung into space by the impact eventually coalesced into the Moon. The catch is that computer simulations of this event don’t often result in a completely molten Moon. So more study is needed. The lunar samples have been under constant scrutiny for the last 50 years, and Smith says he’s interested to see what new information can be gleaned from those samples as new analytical technology is developed.
Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington. The next gathering is set for Wednesday, August 28, 2019 at Peddler Brewing Company in Ballard.