Moon

Over the moon: U of T student lands 'dream' placement making next-gen space robots

Christopher.Sorensen — Wed, 17 Mar 2021 15:40:54 +0000

Over the moon: U of T student lands 'dream' placement making next-gen space robots

Christopher.Sorensen Wed, 03/17/2021 - 11:40

Cutline

U of T Engineering student Erin Richardson is spending 16 months at Canadian space engineering firm MDA, where she is working on a new generation of autonomous robots for the forthcoming Lunar Gateway space station (photo courtesy of MDA)

Tyler Irving

Topic

Our Community

Alumni

Co-op

Faculty of Applied Science & Engineering

Moon

Space

Undergraduate Students

Undergraduate Education

Erin Richardson was in Grade 9 when she decided she wanted to be an astronaut.

“We had a science unit on outer space, and I remember being completely fascinated by the vast scale of it all,” says the third-year engineering science student in the ��Ƶ’s Faculty of Applied Science & Engineering. “Thinking about how big the universe is, and how we’re just a tiny speck on a tiny planet, I knew I wanted to be part of exploring it.”

Richardson started following Canadian astronaut Chris Hadfield on social media and watching videos of his daily life on the International Space Station. She also started reading about aerospace and doing everything she could to break into the industry, including getting her student pilot permit.

It was in a Forbes magazine article about women in STEM that she first heard about Kristen Facciol, a U of T Engineering alumna who had worked as a systems engineer at Canadian space engineering firm MDA before moving on to the Canadian Space Agency (CSA). At the time, Facciol was an Engineering Support Lead that provided real-time flight support during on-orbit operations and teaching courses to introduce astronauts and flight controllers to the ISS robotic systems.

Today, Facciol is a flight controller for CSA/NASA.

“I found her contact information and reached out to her,” says Richardson. “She’s been an amazing mentor to me over the last five years. We’re still close friends, and she’s really helped influence my career path.”

With Facciol’s encouragement, Richardson applied to U of T’s engineering science program, eventually choosing the aerospace major. After her first year, she landed a summer research position in the lab of Jonathan Kelly, an assistant professor at the U of T Institute of Aerospace Studies (UTIAS) who works on simulation tools for a robotic mobile manipulator platform.

“Working in Kelly’s lab piqued my interest in robotics as they could be applied in space,” Richardson says. “Researching collaborative manipulation in dynamic environments will push the boundaries of human spaceflight – during spacewalks, astronauts work right alongside robots all the time.”

After her second year, Richardson travelled to Tasmania for a research placement facilitated by EngSci’s ESROP Global program. Working with researchers at the Commonwealth Scientific and Industrial Research Organisation, Australia’s national science agency, Richardson created tools to analyze data collected during scientific mooring deployments, which help researchers learn more about oceans over long periods of time. This work informs the design of next-generation mooring systems which, like space systems, must survive harsh and constrained environments.

Richardson was sitting in a second-year lecture when she heard the news that Canada had joined NASA’s Lunar Gateway project, a new international space station set to be constructed between 2023 and 2026. Unlike the ISS, which currently orbits Earth, the Lunar Gateway will orbit the moon and will serve both as a waypoint for future crewed missions to the lunar surface and as preparation for missions to even more distant worlds, such as Mars.

Energized, Richardson searched for a way to get involved. Her opportunity came in the fall of 2019 when she saw a posting on MDA’s job board. She immediately applied through U of T Engineering’s Professional Experience Year Co-op program, which enables undergraduate students to spend up to 16 months working for leading firms worldwide before returning to finish their degree programs.

Richardson started her placement in May 2020, well into the COVID-19 pandemic. She and her employer quickly adapted.

“I was working from home through the summer, but for my latest project I was able to go on site to operate this robotic arm,” she says.

The robotic arm in question is a model of Dextre, a versatile robot that maintains the International Space Station. Richardson used it as a prototype part for the Canadarm3, which will be installed on Lunar Gateway.

Because the Lunar Gateway will be so far from Earth, Canadarm3 will be designed to execute certain tasks without supervision from a remote control station. Part of Richardson’s job is to create the dataset that will eventually be used to train the artificial intelligence algorithms that will make this possible.

In MDA’s DREAMR lab, Richardson guided the robotic arm through a series of movements and scenarios, with a suite of video cameras tracking its every move. She then tagged each series of images with metadata that will teach the robot whether the movements it saw were desirable ones to emulate, or dangerous ones to avoid.

“We had to capture different lighting conditions and obstacles of various sizes and colours,” she says. “My colleagues pointed out to me that because it’s me deciding which scenarios count as collisions and which ones don’t, the AI that we eventually create will be a reflection of my own brain.”

Apart from the opportunity to contribute to the next generation of space robots, Richardson says she’s enjoyed the chance to apply what she’s learned in her U of T classes, as well as the professional connections she’s made.

“It’s my dream job,” she says. “I use what I learned in engineering design courses every day. I’m treated as a full engineer and a member of the team. The people I work with are extremely supportive and they talk to me about my dreams and goals. I love being surrounded by a team of talented and motivated people – all so passionate about what they do and about advancing space exploration.

“It’s an awesome opportunity for any student.”

A suitcase full of moon rocks: Working with NASA, U of T's David Strangway brought a piece of Apollo 11 to Toronto

Christopher.Sorensen — Fri, 19 Jul 2019 17:24:58 +0000

A suitcase full of moon rocks: Working with NASA, U of T's David Strangway brought a piece of Apollo 11 to Toronto

Christopher.Sorensen Fri, 07/19/2019 - 13:24

Cutline

More than 3,000 people lined up for a peek at a moon rock and a thimbleful of moon dust when they went on display on campus (photo courtesy of U of T Mississauga)

Topic

For at least one day in Grade 2, Susan Strangway was unquestionably the most popular girl in school.

Her dad, David Strangway, was a ��Ƶ geophysicist who worked for NASA beginning in the mid-to-late 1960s – just as the space agency worked toward the first manned trips to the moon.

Strangway, who would go on to serve as U of T’s president, was part of the team that organized and oversaw the preservation of moon rocks, and he brought some to Susan’s school for a day of show-and-tell that made the local papers in the fall of 1969.

“He was like a movie star,” Susan told U of T News.

A local newspaper reported the U of T professor brought the moon samples to the school under police guard. “Dr. Strangway told us that the questions asked by his son’s Grade 5 classmates were as fine a group of questions as he’s ever been asked by adults,” the then-principal Donald Cooper was quoted as saying.

Fan mail from children to David Strangway after he visited his daughter’s Toronto elementary school with samples of moon rocks and dust (photo courtesy of Susan Strangway)

With the 50th anniversary of the Apollo 11 moon landing this weekend, Susan and her sister Patricia, who both live in B.C., spoke to U of T News about their father’s role at NASA and his time at U of T.

Strangway grew up in Angola with his Canadian missionary parents, but later returned to Canada to earn a bachelor's, master's and PhD at U of T. He taught at the University of Colorado and the Massachusetts Institute of Technology before being enticed back to Toronto to take charge of U of T’s geology department.

On the night of July 20, 1969, Strangway watched on TV – with more than 500 million people around the globe – as astronaut Neil Armstrong took his first steps on the moon.

“It was tremendously exciting to realize that the whole world was sitting rooted on this particular event and that before very long, I was actually going to have a piece of that stuff sitting right there; being able to measure something I’d always dreamed about being able to measure,” Strangway recalled in an interview with the Toronto Star in 1994.

After the historic moon landing, Armstrong, Edwin “Buzz” Aldrin and Michael Collins returned to Earth with about 21.5 kilograms of moon rocks and dust – some of which eventually came to Canada in Strangway’s luggage.

His daughters say their father packed the moon samples in his suitcase, the dust kept in glass jars and the rocks wrapped in dirty laundry.

The Strangway family at NASA in Houston, Tex. From left: Richard, Alice, David, Patricia, David's mom Alice and Susan (photo courtesy of Susan Strangway)

The extraterrestrial material presented Canadian customs agents with a conundrum. His daughters say that Strangway answered honestly when asked if he had anything to declare. “He said, ‘I’ve got a bunch of moon rocks and they waved him through,” Patricia said. His declaration form apparently read, in part: “No. of packages: one; Contents: moondust; Appraised value: NCV (no commercial value) ... Place of Origin: Moon.”

When customs officials later realized Strangway was telling the truth, they visited him at home. The government eventually issued him a “certificate of importation of foreign soil,” he told the Star.

Strangway’s involvement with NASA didn’t end there. In 1970, he became head of the geophysics branch of NASA during the peak years of the Apollo program. He was involved in designing experiments, training astronauts to collect samples and helping choose a landing site for lunar modules. He received NASA's medal for exceptional scientific achievement two years later.

Left to right: Associate Dean Irving Spiegel, geophysicist David Strangway, Principal J. Tuzo Wilson, and Dean E.A. Robinson (photo by Robert Lansdale/��Ƶ Archives)

When he became chair of U of T’s geology department after his years with NASA, Strangway helped land a $1-million federal grant and an expansion of the department’s faculty and equipment. He established a Physical Properties Laboratory at Erindale College, now U of T Mississauga, where researchers investigated magnetic and electromagnetic properties of rocks – including moon rocks.

He brought back $500,000 worth of NASA equipment on a long-term loan that was later entirely forgiven, according to the Vancouver Sun.

When the first lunar samples arrived in Canada and were exhibited on campus, more than 3,000 people lined up for a peek at a moon rock that was smaller than a golf ball and a thimbleful of moondust. The samples were encased in a glass receptacle designed by the jeweller, Birks.

A moon rock and vial of moon dust on display at U of T in a glass orb designed by the jeweller Birks (photo courtesy of U of T Mississauga)

Strangway went on to serve as U of T President from 1983 to 1984 before taking the reins at the University of British Columbia for 12 years.

His work on the Apollo program earned him celebrity status “everywhere he went for the rest of his life,” according to daughter Patricia.

“Despite all his illustrious accomplishments, people really are fascinated by the Apollo missions, as you can see 50 years later.”

Strangway’s work with NASA remains a source of pride for his children, whose own kids have read about his accomplishments in textbooks. Earlier this week when Susan looked at the full moon, she thought of her dad.

“You brought me some of that.”

Mark the 50th anniversary of the Apollo 11 moon landing with these words from U of T’s Marshall McLuhan

Romi Levine — Thu, 18 Jul 2019 18:27:07 +0000

Mark the 50th anniversary of the Apollo 11 moon landing with these words from U of T’s Marshall McLuhan

Romi Levine Thu, 07/18/2019 - 14:27

Cutline

Visitors admire Neil Armstrong's Apollo 11 spacesuit this week after it was unveiled for the first time in 13 years at the Smithsonian National Air and Space Museum in Washington, D.C. (Photo by Alastair Pike/AFP/Getty Images)

Topic

On July 21, 1969, people around the world crowded around their televisions to witness history in the making: astronaut Neil Armstrong taking his first steps on the moon.

The United States’ Apollo 11 spacecraft landed on the moon the day before – becoming the first crewed vessel to do so.

The momentous occasion sparked a lively conversation on U.S. television network ABC’s As it Happens between U of T Professor and famed media theorist Marshall McLuhan, Scottish landscape architect and writer Ian McHarg, Newsday publisher Bill Moyers and journalist Howard K. Smith.

Watch the full conversation here:

The panel discussed the significance of the moon landing – from debating whether it was a conquest versus an exploratory mission to the space race with Russia.

McLuhan was looking to the future in order to gauge the long-term benefits of the moon landing.

“Let’s ask ourselves in long-term projects about the meteorological possibilities of the conquest of moon space,” he said. “Can we consider the possibility of space platforms that might serve the control of climatic conditions eventually on Earth?”

He also predicted that transportation – from space travel to cars – will soon become obsolete in their current forms.

“We can tell by saturation and pollution that we’re reaching a terminus in many areas of use of materials,” he said.

And the biggest shift that will take place once man has explored the moon?

“The hidden change created by moonshot is a totally new environment for human knowledge,” he said.

What the moon's craters reveal about the Earth's history: U of T expert and lead author of new study

noreen.rasbach — Fri, 18 Jan 2019 17:36:40 +0000

What the moon's craters reveal about the Earth's history: U of T expert and lead author of new study

noreen.rasbach Fri, 01/18/2019 - 12:36

Cutline

A look at the southern rim of the Copernicus crater on the moon (photo by NASA/GSFC/Arizona State University)

Sara Mazrouei

Topic

Global Lens

Earth Sciences

Faculty of Arts & Science

Global

Moon

Research & Innovation

Most scientists believe the rate at which the moon and Earth have been bombarded by meteorites has remained constant for the past two to three billion years. Understanding the age of craters on the moon can help us better understand the age of our own planet because the Earth would have received similar numbers of impacts.

It’s been assumed that the rarity of young craters on Earth (those created 300 to 600 million years ago) is attributed to preservation bias – craters have been erased over the years by erosion and the movement of the Earth’s plates. Since then, however, using a new method to date craters on the moon, my colleagues and I have determined that the rarity of craters 300 to 600 million years old is due to a lower bombardment rate. In fact, the bombardment rate has increased by a factor of two to three in the past 300 million years.

To test this idea, we compared the Earth’s crater record to the moon’s in an article published in the journal Science . We suggest that the scarcity of terrestrial craters that are 300 to 650 million years old is simply due to a lower bombardment rate during that period – and not due to preservation bias.

Using rock abundance data from the Lunar Reconnaisance Orbiter to determine ages for lunar craters (image by Rebecca Ghent, ��Ƶ, and Thomas Gernon, University of Southampton)

Dating craters

The moon’s surface serves as a time capsule, helping us to detangle Earth’s history. There are tens of thousands of craters on the moon and the only way to see if the bombardment rate has changed is to have an age for every single crater.

Stable terrain and crater erosion

Analysis shows young craters with numerous metre-sized fragments are easy to pick out from older craters with eroded fragments. As time goes by, these large rocks get broken down by future small impactors. Eventually, over the course of about a billion years, all of the rocks form into lunar regolith (a fine layer of dust covering the moon’s surface), providing an inverse relationship between rock abundance (the rockiness of a crater’s ejecta) and crater age. As craters get older, they become less rocky.

Using measured rock abundance values, we computed ages for 111 lunar rocky craters larger than 10 kilometres in diameter that formed between 80°N and 80°S over the last billion years. Using the ages of these young craters, we determined that the production rate of large lunar craters (more than 10 kilometres in diameter) increased by a factor of two to three in the past ~300 million years. Thus, the near-Earth objects population has increased over the last billion years.

The size and age distributions of lunar and terrestrial craters larger than 20 kilometres over the last 650 million years have similar shapes. This implies that large crater erasure must be limited on stable terrestrial terrains. It also implies that the observed deficit of large terrestrial craters between 290 and 650 million years is not preservation bias, but a reflection of a distinctly lower impact rate. If we had observed more dominant erosion, the age distribution of terrestrial craters would be strongly skewed toward younger ages.

Using data from the recent study on moon craters, SYSTEM Sounds created this video and accompanying soundtrack

Support for limited erosion on cratered terrains also comes from records of kimberlite pipes on Earth. Kimberlite pipes are carrot-shaped pipes that extend a couple of kilometres below the surface and are often located on the same stable regions where we would find preserved impact craters. These underground pipes have been widely mined for diamonds, providing scientists with plentiful information about their location and erosion state.

Records show that kimberlite pipes have not experienced much erosion since forming around 650 million years ago. Therefore, the large young impact craters found on the same stable terrains must also be intact, providing us with a complete record.

Asteroid breakup?

The cause of this increase in the bombardment rate is still unknown. However, a hypothesis is that an asteroid family breakup caused a larger amount of debris to leave the asteroid belt and head towards our region of the Solar System. The loss of most craters older than 650 million years could be due to erosion from Snowball Earth, when most of Earth’s surface was frozen around 650 million years ago.

We predict that the rare extinction-level event type craters like Chicxulub, which may have lead to the extinction of the dinosaurs, were a byproduct of the current high bombardment rate. These new findings could have implications for the evolution of Phanerozoic life — our current geologic era — and the history of life including extinction events and evolution of new species.

Sara Mazrouei is a sessional lecturer and planetary scientist at the ��Ƶ.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Team of scientists led by U of T identify period of increased asteroid impacts on ancient Earth by studying the moon

noreen.rasbach — Thu, 17 Jan 2019 16:22:25 +0000

Team of scientists led by U of T identify period of increased asteroid impacts on ancient Earth by studying the moon

noreen.rasbach Thu, 01/17/2019 - 11:22

Cutline

The image shows a map of all the lunar craters included in this study, with small images showing the study craters at their respective sizes relative to Copernicus, pictured at the top (data from NASA GSFC / LRO / USGS; image by Alex Parker)

Arts & Science news staff

Topic

Global Lens

Earth Sciences

Faculty of Arts & Science

Global

Graduate Students

Moon

Research & Innovation

An international team of scientists is challenging our understanding of a part of Earth’s history by looking at the moon, the most complete and accessible chronicle of the asteroid collisions that carved our solar system.

In a study published today in Science, the team shows the number of asteroid impacts on the moon and Earth increased by two to three times starting around 290 million years ago.

“Our research provides evidence for a dramatic change in the rate of asteroid impacts on both Earth and the moon that occurred around the end of the Paleozoic era,” said lead author Sara Mazrouei, who recently earned her PhD in the department of Earth sciences in the ��Ƶ’s Faculty of Arts & Science.

“The implication is that since that time we have been in a period of relatively high rate of asteroid impacts that is 2.6 times higher than it was prior to 290 million years ago.”

It had previously been assumed that most asteroid-produced craters on the Earth older than 290 million years had been erased by erosion and other geologic processes. But the new research shows otherwise.

“The relative rarity of large craters on Earth older than 290 million years and younger than 650 million years is not because we lost the craters, but because the impact rate during that time was lower than it is now,” said Rebecca Ghent, an associate professor in U of T’s department of Earth sciences and one of the paper’s co-authors. “We expect this to be of interest to anyone interested in the impact history of both Earth and the moon, and the role that it might have played in the history of life on Earth.”

Scientists have for decades tried to understand the rate that asteroids hit Earth by using radiometric dating of the rocks around craters to determine their ages. But because it was believed erosion caused some craters to disappear, it was difficult to find an accurate impact rate and determine whether it had changed over time.

This image depicts the method by which the Diviner instrument on the Lunar Reconnaissance Orbiter senses the heat emanating from the lunar surface, which allows scientists to map the abundance of rocks around young impact craters. The team used this information to estimate ages for lunar craters larger than 10 kilometres in diameter. Young craters have lots of rocks near their rims, and those rocks break down into smaller particles over time, disappearing from the Diviner thermal data (data plots by Rebecca Ghent; illustration by Thomas Gernon)

A way to sidestep this problem is to examine the moon, which is hit by asteroids in the same proportions over time as Earth. But there was no way to determine the ages of lunar craters until NASA’s Lunar Reconnaissance Orbiter (LRO) started circling the moon a decade ago and studying its surface.

“The LRO’s instruments have allowed scientists to peer back in time at the forces that shaped the moon,” said Noah Petro, an LRO project scientist based at NASA Goddard Space Flight Center.

Using LRO data, the team was able to assemble a list of the ages of all lunar craters younger than about a billion years. They did this by using data from LRO’s Diviner instrument, a radiometer that measures the heat radiating from the moon’s surface, to monitor the rate of degradation of young craters.

During the lunar night, rocks radiate much more heat than fine-grained soil called regolith. This allows scientists to distinguish rocks from fine particles in thermal images. Ghent had previously used this information to calculate the rate at which large rocks around the moon’s young craters – ejected onto the surface during asteroid impact – break down into soil over tens of millions of years. By applying this idea, the team was able to calculate ages for previously undated lunar craters.

When compared to a similar timeline of Earth’s craters, they found the two bodies had recorded the same history of asteroid bombardment.

“It became clear that the reason why Earth has fewer older craters on its most stable regions is because the impact rate was lower up until about 290 million years ago,” said William Bottke, an asteroid expert at the Southwest Research Institute in Boulder, Colo., and another of the paper’s co-authors. “The answer to Earth’s impact rate was staring everyone right in the face.”

The reason for the jump in the impact rate is unknown, though the researchers speculate it might be related to large collisions taking place more than 300 million years ago in the main asteroid belt between the orbits of Mars and Jupiter. Such events can create debris that can reach the inner solar system.

Ghent and her colleagues found strong supporting evidence for their findings through a collaboration with Thomas Gernon, an Earth scientist based at the University of Southampton in England who works on a terrestrial feature called kimberlite pipes. These underground pipes are long-extinct volcanoes that stretch, in a carrot shape, a couple of kilometres below the surface, and are found on some of the least eroded regions of Earth in the same places that preserved impact craters are found.

“The Canadian Shield hosts some of the best-preserved and best-studied of this terrain – and also some of the best-studied large impact craters,” said Mazrouei.

Gernon showed that kimberlite pipes formed over the past 650 million years had not experienced much erosion, indicating that large impact craters younger than this on stable terrains must also be intact.

“This is how we know those craters represent a near-complete record,” Ghent said.

While the researchers weren’t the first to propose that the rate of asteroid strikes to Earth has fluctuated over the past billion years, they are the first to show it statistically and to quantify the rate.

“The findings may also have implications for the history of life on Earth, which is punctuated by extinction events and rapid evolution of new species,” said Ghent. “Though the forces driving these events are complicated and may include other geologic causes, such as large volcanic eruptions, combined with biological factors, asteroid impacts have surely played a role in this ongoing saga.

“The question is whether the predicted change in asteroid impacts can be directly linked to events that occurred long ago on Earth.”

The findings are described in the study “Earth and Moon impact flux increased at the end of the Paleozoic,” published in Science. Support for the research was provided by the National Science and Engineering Research Council of Canada, NASA’s Solar System Exploration Research Virtual Institute, and the Natural Environment Research Council of the United Kingdom.

With files from NASA

Cool while it lasted: U of T astronomer explains science behind "supermoon"

ullahnor — Tue, 15 Nov 2016 20:02:05 +0000

Cool while it lasted: U of T astronomer explains science behind "supermoon"

ullahnor Tue, 11/15/2016 - 15:02

Cutline

The supermoon is seen rising behind the Soyuz rocket at the Baikonur Cosmodrome launch pad in Kazakhstan Nov. 14 (photo credit Bill Ingalls/NASA via Flickr)

Noreen Ahmed-Ullah

Author legacy

Noreen Ahmed-Ullah

Topic

Global Lens

Astronomy

Dunlap Institute for Astronomy & Astrophysics

Moon

Science

If you had a chance to look to the skies this week and take in the magnificent “supermoon,” you may have wondered about the science behind the phenomenon.

U of T News spoke to Renée Hložek, an assistant professor of astronomy in the Faculty of Arts & Science. Hložek, who is also appointed to the Dunlap Institute for Astronomy & Astrophysics, is a TED expert who reaches thousands of people with her videos, making science accessible and fun for the average person.

She thinks the supermoon is a bit overhyped. But, for those of us who usually just gaze in awe, she broke down the science behind it.

The "supermoon" over Toronto Monday (photo by mark.watmough via Flickr)

What is the “supermoon”?

The term "supermoon" just describes the fact that the moon is both a full moon, and is at the point in its orbit that is closest to us. It appears a bit bigger and brighter in the sky, but only around 10 per cent.

It is lovely to see the moon in the sky, but it is sometimes the case that the supermoon is overhyped. For example, the tides will be higher because the moon is closer to us, but lots of questions that I'm getting are about things like the moon and the New Zealand earthquake, which are definitely not related!

The moon will appear a little more orange around sunset as it catches the last of the sun's rays. One of the cool things is that the Earth-moon orbit is actually very close to circular, but it is closer at different times in its orbit. The reason why it is "super" is because it is reasonably rare that the Earth is close and full at the same time – which is why we won't see another moon this close during a full moon until 2048.

What's creating the phenomenon?

The phenomenon is due to the orbit of the moon around the Earth, which changes its distance to us ever so slightly and generates the phase of the moon, which now is full.

The moon looks the brightest near sunset. It always appears bigger when it is near the horizon.

Any other celestial phenomena we should be looking out for in the coming weeks/months?

The Leonid meteor shower is coming up on Nov. 17/18, so that is something to look out for late on the 17th and in the early hours of the 18th. It's fun to see how many shooting stars you can see that night, and to take the chance to enjoy the night sky more generally.

Moon

Over the moon: U of T student lands 'dream' placement making next-gen space robots

A suitcase full of moon rocks: Working with NASA, U of T's David Strangway brought a piece of Apollo 11 to Toronto

Mark the 50th anniversary of the Apollo 11 moon landing with these words from U of T’s Marshall McLuhan

Watch the full conversation here:

What the moon's craters reveal about the Earth's history: U of T expert and lead author of new study

Dating craters

Read more about the research at U of T News

Stable terrain and crater erosion

Asteroid breakup?

Team of scientists led by U of T identify period of increased asteroid impacts on ancient Earth by studying the moon

Cool while it lasted: U of T astronomer explains science behind "supermoon"

Read more about Hložek