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Life, as we all know, is based on chemistry. Prebiotic chemical building blocks existed on our planet for a long time before life arose. Astrobiology and cosmochemistry focus on the formation of those building blocks. They also look at the role each played in creating all the life forms we know today.

For a long time, cosmo-chemists have known that organic molecules called polycyclic aromatic hydrocarbons (PAHs) are quite plentiful in the Universe. Scientists consider them plausible prebiotic building blocks that likely played an important role in the formation of life on Earth. What’s not as well understood is their origin story. For a long time, scientists suspected that they formed in regions where temperatures get to around 1000 K. That would supply energy to promote chemical activity to create PAHs, such as in star-forming molecular clouds or circumstellar disks. It’s also possible they form as part of the processing of carbon-rich dust grains by nearby energy sources (such as stars).

However, based on recent studies of an asteroid and meteorite, it turns out that some PAHs formed in cold regions of space, too. In those regions, the temperature does not get much higher than 100 K. That finding opens up new pathways for understanding life’s chemical journey on other planets and celestial bodies.

Understanding These Organic Molecules

According to Professor Kliti Grice, a researcher at the Western Australia Organic and Isotope Geochemistry Centre at Curtin University, understanding these materials is a big step. “PAHs are organic compounds made up of carbon and hydrogen that are common on Earth but are also found in celestial bodies like asteroids and meteorites,” said Grice.

They’re spread throughout the interstellar medium and detected in galaxies across the Universe. Generally, they’re used as a tracer of cold molecular gas, which is where stars—and planets—begin their formation journey.

An image of an interstellar nebula with some polycyclic aromatic hydrocarbon (PAH) molecular structures superimposed. These organic molecules exist throughout the Universe.
Courtesy: NASA.

As such, scientists want to trace their path from space to Earth and compare space-based PAHs to Earth-based ones. That’s because PAHs are a very likely precursor to the kinds of materials that eventually lead to the formation of life. That makes their presence on other celestial bodies intriguing as scientists work to understand the formation and evolution of life.

Beyond Earth, PAHs account for about 30 percent of all carbon found in regions around stars, in molecular clouds, and on planets (and other bodies). On Earth, many PAHs exist in coal deposits and oil reservoirs. Plants burning (as in forest fires) also produce these compounds. They work their way into the soil and eventually end up in plants (among other things).

Organic Molecules and Rocky Bodies

Grice is part of an international research team that focused on pieces of asteroid Ryugu and the famous Murchison meteorite to figure out where their PAHs formed. The team started with an unusual chemistry project: burning plants. That’s because plants contain PAHs that form here on Earth. “We performed controlled burn experiments on Australian plants,” said Grice, “which were isotopically compared to PAHs from fragments of the Ryugu asteroid that were returned to Earth by a Japanese spacecraft in 2020, and the Murchison meteorite that landed in Australia in 1969. The bonds between light and heavy carbon isotopes in the PAHs were analyzed to reveal the temperature at which they were formed.”

The Murchison Meteorite, which fell to  Earth in 1969. Courtesy Basilicofresco, CC BY-SA 3.0
The Murchison Meteorite, which fell to Earth in 1969. It contains organic molecules. Courtesy Basilicofresco, CC BY-SA 3.0

Using high-tech methods to study Ryugu and Murchison, the team found two sources of PAHs with slightly different characteristics. “The smaller ones likely formed in cold outer space, while bigger ones probably formed in warmer environments, like near a star or inside a celestial body,” according to Grice.

Ryugu is particularly interesting since it formed early in the Solar System’s history. A critical analysis of its chemistry found several PAHs. The team also detected organosulfides (compounds with sulfur). These all likely formed in very cold interstellar

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Stellar Winds Coming From Other Stars Measured for the First Time

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An international research team led by the University of Vienna has made a major breakthrough. In a study recently published in Nature Astronomy, they describe how they conducted the first direct measurements of stellar wind in three Sun-like star systems. Using X-ray emission data obtained by the ESA’s X-ray Multi-Mirror-Newton (XMM-Newton) of these stars’ “astrospheres,” they measured the mass loss rate of these stars via stellar winds. The study of how stars and planets co-evolve could assist in the search for life while also helping astronomers predict the future evolution of our Solar System.

The research was led by Kristina G. Kislyakova, a Senior Scientist with the Department of Astrophysics at the University of Vienna, the deputy head of the Star and Planet Formation group, and the lead coordinator of the ERASMUS+ program. She was joined by other astrophysicists from the University of Vienna, the Laboratoire Atmosphères, Milieux, Observations Spatiales (LAMOS) at the Sorbonne University, the University of Leicester, and the Johns Hopkins University Applied Physics Laboratory (JHUAPL).

Astrospheres are the analogs of our Solar System’s heliosphere, the outermost atmospheric layer of our Sun, composed of hot plasma pushed by solar winds into the interstellar medium (ISM). These winds drive many processes that cause planetary atmospheres to be lost to space (aka. atmospheric mass loss). Assuming a planet’s atmosphere is regularly replenished and/or has a protective magnetosphere, these winds can be the deciding factor between a planet becoming habitable or a lifeless ball of rock.

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Logarithmic scale of the Solar System, Heliosphere, and Interstellar Medium (ISM). Credit: NASA-JPL

While stellar winds mainly comprise protons, electrons, and alpha particles, they also contain trace amounts of heavy ions and atomic nuclei, such as carbon, nitrogen, oxygen, silicon, and even iron. Despite their importance to stellar and planetary evolution, the winds of Sun-like stars are notoriously difficult to constrain. However, these heavier ions are known to capture electrons from neutral hydrogen that permeates the ISM, resulting in X-ray emissions. Using data from the XXM-Newton mission, Kislyakova and her team detected these emissions from other stars.

These were 70 Ophiuchi, Epsilon Eridani, and 61 Cygni, three main sequence Sun-like stars located 16.6, 10.475, and 11.4 light-years from Earth (respectively). Whereas 70 Ophiuchi and 61 Cygni are binary systems of two K-type (orange dwarf) stars, Epsilon Eridani is a single K-type star. By observing the spectral lines of oxygen ions, they could directly quantify the total mass of stellar wind emitted by all three stars. For the three stars surveyed, they estimated the mass loss rates to be 66.5±11.1, 15.6±4.4, and 9.6±4.1 times the solar mass loss rate, respectively.

In short, this means that the winds from these stars are much stronger than our Sun’s, which could result from the stronger magnetic activity of these stars. As Kislyakova related in a University of Vienna news release:

“In the solar system, solar wind charge exchange emission has been observed from planets, comets, and the heliosphere and provides a natural laboratory to study the solar wind’s composition. Observing this emission from distant stars is much more tricky due to the faintness of the signal. In addition to that, the distance to the stars makes it very difficult to disentangle the signal emitted by the astrosphere from the actual X-ray emission of the star itself, part of which is “spread” over the field-of-view of the telescope due to instrumental effects.”

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XMM-Newton X-ray image of the star 70 Ophiuchi (left) and
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How to Know How Hard a Hike Will Be

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By Michael Lanza

“How hard will that hike be?” That’s a question that
all dayhikers and backpackers, from beginners to experts, think about all the
time—and it’s not always easy to answer. But there are ways of evaluating the
difficulty of any hike, using readily available information, that can greatly
help you understand what to expect before you even leave home. Here’s
how.

No matter how relatively easy or arduous the hike you’re considering, or where you fall on the spectrum of hiking experience or personal fitness level, this article will tell you exactly how to answer that question—and which questions to ask and what information to seek to reach that answer. This article shares what I’ve learned over four decades of backpacking and dayhiking, including the 10 years I spent as a field editor for Backpacker magazine and even longer running this blog, and this knowledge can help ensure that you and your companions or your family don’t get in over your heads.

Whether you’re new to dayhiking or backpacking, a
parent planning a hike with young kids, or a fit and experienced dayhiker or
backpacker contemplating one of the toughest hikes you’ve ever attempted, it’s
important to have a good sense of what you’ll face on a new and unfamiliar hike
and whether it’s within your abilities.

Tet19 047 Me on Teton Crest Trail copy cropped 17 jpg
Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-books to classic backpacking trips. Click here to learn how I can help you plan your next trip.

A backpacker hiking the Dawson Pass Trail in Glacier National Park.
” data-image-caption=”Pam Solon backpacking the Dawson Pass Trail in Glacier National Park. Click photo to read about backpacking in Glacier.
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/12/06224534/Gla7-117-Pam-Solon-backpacking-the-Dawson-Pass-Trail-in-Glacier-National-Park.jpg?fit=300%2C200&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/12/06224534/Gla7-117-Pam-Solon-backpacking-the-Dawson-Pass-Trail-in-Glacier-National-Park.jpg?fit=900%2C600&ssl=1″ src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/12/06224534/Gla7-117-Pam-Solon-backpacking-the-Dawson-Pass-Trail-in-Glacier-National-Park-1024×683.jpg?resize=900%2C600&ssl=1″ alt=”A backpacker hiking the Dawson Pass Trail in Glacier National Park.” class=”wp-image-61235″ srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/12/06224534/Gla7-117-Pam-Solon-backpacking-the-Dawson-Pass-Trail-in-Glacier-National-Park.jpg 1024w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/12/06224534/Gla7-117-Pam-Solon-backpacking-the-Dawson-Pass-Trail-in-Glacier-National-Park.jpg 300w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/12/06224534/Gla7-117-Pam-Solon-backpacking-the-Dawson-Pass-Trail-in-Glacier-National-Park.jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/12/06224534/Gla7-117-Pam-Solon-backpacking-the-Dawson-Pass-Trail-in-Glacier-National-Park.jpg 150w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/12/06224534/Gla7-117-Pam-Solon-backpacking-the-Dawson-Pass-Trail-in-Glacier-National-Park.jpg 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />Pam Solon backpacking the Dawson Pass Trail in Glacier National Park. Click photo to read about backpacking in Glacier.

Exceeding your limits or those of someone with you can
invite unwanted consequences—and the person with the least stamina,
abilities, or experience often dictates any party’s pace, limits, and outcomes.
Those consequences
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The 12 Best Down Jackets of 2024

Tet19 047 Me on Teton Crest Trail copy cropped 14 jpg

By Michael Lanza

Whatever you need an insulated jacket for, there’s a down or synthetic puffy for your needs, within your budget. And whether you want a puffy jacket for outdoor activities like backpacking, camping, skiing, climbing, and hut treks, or just to keep you warm around town or at outdoor sporting events, this review will help you figure out how to choose the right jacket for your purposes, and it spotlights the best down and synthetic insulated jackets available today.

I selected the jackets covered in this review after extensive testing on backpacking, camping, backcountry ski touring, climbing and other backcountry trips. I’ve field-tested dozens of insulated jackets over nearly three decades of testing and reviewing gear, formerly as the lead gear reviewer for Backpacker magazine for 10 years and even longer running this blog.

Technology has blurred the traditional lines between down and synthetics, with water-resistant down that traps heat even when wet—all but eliminating the weakness that had long been the Achilles heel of down—and synthetic insulation materials that approach the warmth-to-weight ratio and compressibility of down.

If you’d prefer, scroll past my buying tips to dive immediately into the jacket reviews.

If you have a question for me or a comment on this review, please leave it in the comments section at the bottom of this story. I try to respond to all comments.

Tet19 047 Me on Teton Crest Trail copy cropped 15 jpg
Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-guides to classic backpacking trips. Click here to learn how I can help you plan your next trip.

The Black Diamond Approach Down Hoody.
” data-image-caption=”The Black Diamond Approach Down Hoody in the Grand Canyon.
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2022/04/06225653/Black-Diamond-Approach-Down-Hoody-hood-up-1.jpg?fit=300%2C200&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2022/04/06225653/Black-Diamond-Approach-Down-Hoody-hood-up-1.jpg?fit=900%2C600&ssl=1″ src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2022/04/06225653/Black-Diamond-Approach-Down-Hoody-hood-up-1-1024×683.jpg?resize=900%2C600&ssl=1″ alt=”The Black Diamond Approach Down Hoody.” class=”wp-image-52287″ srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2022/04/06225653/Black-Diamond-Approach-Down-Hoody-hood-up-1.jpg 1024w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2022/04/06225653/Black-Diamond-Approach-Down-Hoody-hood-up-1.jpg 300w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2022/04/06225653/Black-Diamond-Approach-Down-Hoody-hood-up-1.jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2022/04/06225653/Black-Diamond-Approach-Down-Hoody-hood-up-1.jpg 150w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2022/04/06225653/Black-Diamond-Approach-Down-Hoody-hood-up-1.jpg 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />The Black Diamond Approach Down Hoody in the Grand Canyon.

How to Choose a Synthetic or Down Jacket

Insulated jackets today differ not only in type and amount of insulation, but also in water resistance, breathability, and as always, design features like the hood and pockets. When choosing between down and synthetic models, consider the usual conditions and temperatures in which you’ll use it—in other words, how wet and cold you expect to get, and your body type (how easily you get cold)—as well as the seasonal and activity versatility you require. Some questions to
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