ESA/Rosetta/NAVCAM via Flickr // CC BY-SA IGO 3.0
ESA/Rosetta/NAVCAM via Flickr // CC BY-SA IGO 3.0

Comet 67P Transformed as It Approached the Sun

ESA/Rosetta/NAVCAM via Flickr // CC BY-SA IGO 3.0
ESA/Rosetta/NAVCAM via Flickr // CC BY-SA IGO 3.0

Comet 67P/Churyumov-Gerasimenko underwent some fantastic transformations as it approached the Sun, according to a new study of Rosetta data published this week in Science. Fractures grew, cliffs collapsed, and boulders rolled on the comet, among other geologic happenings. 

At the 48th Lunar and Planetary Science Conference in The Woodlands, Texas, Ramy El-Maarry of the University of Colorado, Boulder, revealed stunning images of the comet’s transformation as it approached perihelion, or the closest it gets to the Sun during its orbit. This is the first time scientists have observed in detail the punishment comets sustain this close to the Sun.

“This is the first mission that we’ve been able to have such a huge set of high-resolution images while at the same time having the longevity of a mission where we were able to look at a comet and study how it evolved through more than two years as it journeyed through the inner solar system,” El-Maarry said at the conference. He is a member of the U.S. Rosetta science team and lead author of the study.

From August 2014 through September 2016, Rosetta orbited 67P, its scientific instruments trained on the comet. Then the team attempted to land—and most likely crashed—the orbiter into the comet. Rosetta's fate remains unknown. But the data it sent back to Earth is not.

For the current study, the researchers focused on observations made between December 2014 and June 2016. Among the most striking phenomena they found is a collapsed cliff face, whose volume is the equivalent of nine Olympic-sized swimming pools.

A cliff collapse the researchers observed. Image Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

 
It fell not in a few giant pieces, but essentially crumbled apart, much in the way the White Cliffs of Dover in the United Kingdom sometimes fall. “It would have been like watching a slow-motion video,” El-Maarry told mental_floss. “If you saw the cliff starting to fall, and you’re on the comet, you would have had time to take out your phone, open the camera, start the video and keep recording for 20 or 30 minutes as the event unfolds.”

The collapse revealed bright, fresh, icy comet interior. It's the first time we've observed this process.

At the comet’s nucleus, outbursts caused by increased sunlight moved a 282-million-pound, 100-foot-wide boulder the distance of one and a half football fields. In a cometary day on 67P, an hour and half of perpendicular illumination can cause chaos. In the span of 20 minutes, temperatures swing from -140°C to 50°C. Interior ice sublimates―changes from solid to gas without bothering to become water―and blasts into space. Increased temperatures as the comet approached the Sun also caused Empire State Building–sized fractures along the neck of the rubber duck–shaped body.

Two images showing the boulder's movement. In the right image, the dotted circle outlines the original location of the boulder for reference. Image Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

 
These Rosetta data are the first direct link between outbursts and crumbling cometary material, and suggest that thermal gradients are fundamental drivers of geologic processes on comets, which include weathering and erosion, sublimation of water ice, and mechanical stresses arising from the comet's spin.

If you were to stand on the surface of 67P and witness the cliff face collapse, it would be quite an experience. “If you’re in the northern hemisphere, it might be a lot of fun,” said El-Maarry. “You’re seeing a lot of things happening in slow motion. You might be able to see dust coming from the southern hemisphere and falling like volcanic ash on top of you in the north. It would have also had a spectacular view of space because you don’t have an atmosphere.”

In the extremely long term, the processes responsible for fractures on the duck’s neck will cause the comet to split in two―temporarily. “What we can say with a degree of certainty is that it’s not going to explode. It’s going to break,” he described. “And because it’s going to break and separate, the two bodies still have enough gravity to pull themselves together to reattach.”

The next step, El-Maarry says, is to locate more bodies just entering the solar system, as opposed to objects that have been here for dozens of orbits. “What our work implies is that most of the activity seems to happen just as you enter the inner solar system in an inner configuration,” he said. He is interested in the findings from the New Horizons mission after it visits an object in the Kuiper Belt on January 1, 2019. That region is a source of comets, and New Horizons offers a chance at a pristine body before being subjected to heat or sublimation.

“It will be really cool to see what is the topography you’re seeing there. Are you seeing something that’s just a ball of dust and ice as we thought of comets before going to 67P,” El-Maarry wondered, “or are we going to see all this complex geology? This is going to be really very exciting. When you look at New Horizons, no one really thought that Pluto would look as amazing as it did in picture. And that’s what happens with space missions. They just keep surprising us and opening up new frontiers.” 

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Food
New Plant-Based Coating Can Keep Your Avocados Fresh for Twice as Long
Apeel
Apeel

Thanks to a food technology startup called Apeel Sciences, eating fresh avocados will soon be a lot easier. The Bill Gates–backed company has developed a coating designed to keep avocados fresh for up to twice as long as traditional fruit, Bloomberg reports, and these long-lasting avocados will soon be available at 100 grocery stores across the Midwestern U.S. Thirty or so of the grocery stores involved in the limited rollout of the Apeel avocado will be Costcos, so feel free to buy in bulk.

Getting an avocado to a U.S. grocery store is more complicated than it sounds; the majority of avocados sold in the U.S. come from California or Mexico, making it tricky to get fruit to the Midwest or New England at just the right moment in an avocado’s life cycle.

Apeel’s coating is made of plant material—lipids and glycerolipids derived from peels, seeds, and pulp—that acts as an extra layer of protective peel on the fruit, keeping water in and oxygen out, and thus reducing spoilage. (Oxidation is the reason that your sliced avocados and apples brown after they’ve been exposed to the air for a while.) The tasteless coating comes in a powder that fruit producers mix with water and then dip their fruit into.

A side-by-side comparison of a coated and uncoated avocado after 30 days, with the uncoated avocado looking spoiled and the coated one looking fresh
Apeel

According to Apeel, coating a piece of produce in this way can keep it fresh for two to three times longer than normal without any sort of refrigeration of preservatives. This not only allows consumers a few more days to make use of their produce before it goes bad, reducing food waste, but can allow producers to ship their goods to farther-away markets without refrigeration.

Avocados are the first of Apeel's fruits to make it to market, but there are plans to debut other Apeel-coated produce varieties in the future. The company has tested its technology on apples, artichokes, mangos, and several other fruits and vegetables.

[h/t Bloomberg]

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15 Facts About the Summer Solstice
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iStock

It's the longest day of the year in the Northern Hemisphere, so soak up some of those direct sunrays (safely, of course) and celebrate the start of summer with these solstice facts.

1. THIS YEAR IT'S JUNE 21.

June 21 date against a yellow background
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The summer solstice always occurs between June 20 and June 22, but because the calendar doesn't exactly reflect the Earth's rotation, the precise time shifts slightly each year. For 2018, the sun will reach its greatest height in the sky for the Northern Hemisphere on June 21 at 6:07 a.m. Eastern Time.

2. THE SUN WILL BE DIRECTLY OVERHEAD AT THE TROPIC OF CANCER.

A vintage mapped globe showing the Tropic of Cancer
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While the entire Northern Hemisphere will see its longest day of the year on the summer solstice, the sun is only directly overhead at the Tropic of Cancer (23 degrees 27 minutes north latitude).

3. THE NAME COMES FROM THE FACT THAT THE SUN APPEARS TO STAND STILL.

Stonehenge at sunrise.
CARL DE SOUZA, AFP/Getty Images

The term "solstice" is derived from the Latin words sol (sun) and sistere (to stand still), because the sun's relative position in the sky at noon does not appear to change much during the solstice and its surrounding days. The rest of the year, the Earth's tilt on its axis—roughly 23.5 degrees—causes the sun's path in the sky to rise and fall from one day to the next.

4. THE WORLD'S BIGGEST BONFIRE WAS PART OF A SOLSTICE CELEBRATION.

A large bonfire
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Celebrations have been held in conjunction with the solstice in cultures around the world for hundreds of years. Among these is Sankthans, or "Midsummer," which is celebrated on June 24 in Scandinavian countries. In 2016, the people of Ålesund, Norway, set a world record for the tallest bonfire with their 155.5-foot celebratory bonfire.

5. THE HOT WEATHER FOLLOWS THE SUN BY A FEW WEEKS.

Colorful picture of the sun hitting ocean waves.
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You may wonder why, if the solstice is the longest day of the year—and thus gets the most sunlight—the temperature usually doesn't reach its annual peak until a month or two later. It's because water, which makes up most of the Earth's surface, has a high specific heat, meaning it takes a while to both heat up and cool down. Because of this, the Earth's temperature takes about six weeks to catch up to the sun.

6. THOUSANDS OF PEOPLE GATHER AT STONEHENGE TO CELEBRATE.

Rollo Maughfling, the Archdruid of Glastonbury and Stonehenge, conducts a Solstice celebration service for revelers as they wait for the midsummer sunrise at Stonehenge on June 21, 2012, near Salisbury, England.
Rollo Maughfling, the Archdruid of Glastonbury and Stonehenge, conducts a Solstice celebration service for revelers as they wait for the midsummer sunrise at Stonehenge on June 21, 2012, near Salisbury, England.
Matt Cardy, Getty Images

People have long believed that Stonehenge was the site of ancient druid solstice celebrations because of the way the sun lines up with the stones on the winter and summer solstices. While there's no proven connection between Celtic solstice celebrations and Stonehenge, these days, thousands of modern pagans gather at the landmark to watch the sunrise on the solstice.

7. PAGANS CELEBRATE THE SOLSTICE WITH SYMBOLS OF FIRE AND WATER.

Arty image of fire and water colliding.
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In Paganism and Wicca, Midsummer is celebrated with a festival known as Litha. In ancient Europe, the festival involved rolling giant wheels lit on fire into bodies of water to symbolize the balance between fire and water.

8. IN ANCIENT EGYPT, THE SOLSTICE HERALDED THE NEW YEAR.

Stars in the night sky.
iStock

In Ancient Egypt, the summer solstice preceded the appearance of the Sirius star, which the Egyptians believed was responsible for the annual flooding of the Nile that they relied upon for agriculture. Because of this, the Egyptian calendar was set so that the start of the year coincided with the appearance of Sirius, just after the solstice.

9. THE ANCIENT CHINESE HONORED THE YIN ON THE SOLSTICE.

Yin and yang symbol on textured sand.
iStock

In ancient China, the summer solstice was the yin to the winter solstice's yang—literally. Throughout the year, the Chinese believed, the powers of yin and yang waxed and waned in reverse proportion to each other. At the summer solstice, the influence of yang was at its height, but the celebration centered on the impending switch to yin. At the winter solstice, the opposite switch was honored.

10. IN ALASKA, THE SOLSTICE IS CELEBRATED WITH A MIDNIGHT BASEBALL GAME.

Silhouette of a baseball player.
iStock

Each year on the summer solstice, the Alaska Goldpanners of Fairbanks celebrate their status as the most northerly baseball team on the planet with a game that starts at 10:00 p.m. and stretches well into the following morning—without the need for artificial light—known as the Midnight Sun Game. The tradition originated in 1906 and was taken over by the Goldpanners in their first year of existence, 1960.

11. THE EARTH IS ACTUALLY AT ITS FARTHEST FROM THE SUN DURING THE SOLSTICE.

The Earth tilted on its axis.
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You might think that because the solstice occurs in summer that it means the Earth is closest to the sun in its elliptical revolution. However, the Earth is actually closest to the sun when the Northern Hemisphere experiences winter and is farthest away during the summer solstice. The warmth of summer comes exclusively from the tilt of the Earth's axis, and not from how close it is to the sun at any given time. 

12. IRONICALLY, THE SOLSTICE MARKS A DARK TIME IN SCIENCE HISTORY.

Galileo working on a book.
Hulton Archive, Getty Images

Legend has it that it was on the summer solstice in 1633 that Galileo was forced to recant his declaration that the Earth revolves around the Sun; even with doing so, he still spent the rest of his life under house arrest.

13. AN ALTERNATIVE CALENDAR HAD AN EXTRA MONTH NAMED AFTER THE SOLSTICE.

Pages of a calendar
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In 1902, a British railway system employee named Moses B. Cotsworth attempted to institute a new calendar system that would standardize the months into even four-week segments. To do so, he needed to add an extra month to the year. The additional month was inserted between June and July and named Sol because the summer solstice would always fall during this time. Despite Cotsworth's traveling campaign to promote his new calendar, it failed to catch on.

14. IN ANCIENT GREECE, THE SOLSTICE FESTIVAL MARKED A TIME OF SOCIAL EQUALITY.

Ancient Greek sculpture in stone.
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The Greek festival of Kronia, which honored Cronus, the god of agriculture, coincided with the solstice. The festival was distinguished from other annual feasts and celebrations in that slaves and freemen participated in the festivities as equals.

15. ANCIENT ROME HONORED THE GODDESS VESTA ON THE SOLSTICE.

Roman statue of a vestal virgin
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In Rome, midsummer coincided with the festival of Vestalia, which honored Vesta, the Roman goddess who guarded virginity and was considered the patron of the domestic sphere. On the first day of this festival, married women were allowed to enter the temple of the Vestal virgins, from which they were barred the rest of the year.

A version of this list originally ran in 2015.

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