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Earth is perfectly suited for organic life. It stands to reason then that similar worlds orbiting distant stars might also be rich with life. But proving it will be a challenge. One of the better ways to discover extraterrestrial life will be to study the atmospheres of inhabited exoplanets, but Earth is fairly small for a planet and has a thin atmosphere compared to larger worlds. It will be much easier to study the atmospheres of gas planets, but could such worlds harbor life? A new paper in Universe argues it could.

Exobiologists have long argued that we shouldn’t assume all life in the universe will be on planets similar to Earth. The subsurface oceans of Enceladus and Ganymede could support terrestrial life and Titan has a rich methane chemistry that might support exotic life. But most ideas about life require three main ingredients: energy, water, and a surface.

The first two are pretty obvious. Life needs some kind of energy source to survive, whether it be solar or geothermal, and water is the perfect solution to allow complex molecules to interact. But the requirement of a surface is more subtle. It isn’t needed for life to survive, since lots of organisms can spend their entire life in water or air. Instead, it seems to be necessary for life to arise. Surface chemistry is incredibly good at creating large organic molecules, even in space. It likely takes a rocky surface to create the building blocks of life.

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Artist impression of the Galileo probe descending into Jupiter’s atmosphere. Credit: NASA/Ken Hodges

This new paper argues that while surface chemistry might be needed for life to arise in a planetary system, it isn’t needed for life to thrive. The work focuses on warm sub-Neptune worlds. These planets are about 8 – 10 times more massive than Earth and are likely small gas planets with a thick atmosphere but no terrestrial surface. Several of these worlds have been found in the potentially habitable zone of their star, such as K2-18b, which closely orbits a red dwarf star.

The team shows that warm sub-Neptunes such as K2-18b likely have plenty of water and organic molecules needed to create a habitable zone within their atmosphere. And being smaller gas worlds, it is likely that the habitable layer is fairly stable, allowing for any life to remain aloft long enough to reproduce before sinking to the hostile depths below. Similar arguments have been made for the potentially habitable layer of Venus’s atmosphere. But unlike Venus, K2-18b isn’t likely to have a surface. So even though life might survive on a sub-Neptune world, how would it get there?

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Asteroids might seed sub-Neptunes with life. Credit: ESO

Here the team argues that asteroids might come to the rescue. If an exoplanetary system has an unstable asteroid belt, meteorite impacts with the sub-Neptune planet and smaller terrestrial worlds would both be common. This cross-pollination could bring life to a gassy world.

Because sub-Neptunes are fairly common and have thick atmospheres, they will be among the first planets we study for signs of life. While the odds of finding life on these worlds might be a bit long, it’s worth taking a look just because we can.

Reference: Seager, Sara, et al. “Possibilities for an Aerial Biosphere in Temperate Sub Neptune-Sized Exoplanet Atmospheres.” Universe 7.6 (2021): 172.

The post Could Life
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Webb Measures the Weather on a Tidally Locked Exoplanet

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Exploring exoplanet atmospheres in more detail was one task that planetary scientists anticipated during the long wait while the James Webb Space Telescope (JWST) was in development. Now, their patience is finally paying off. News about discoveries of exoplanet atmosphere using data from JWST seems to be coming from one research group or another almost every week, and this week is no exception. A paper published in Nature by authors from a few dozen institutions describes the atmospheric differences between the “morning” and “evening” sides of a tidally locked planet for the first time.

First, let’s clarify what the “morning” and “evening” sides mean. Tidally locked planets don’t spin, so one hemisphere constantly faces the planet’s star. As such, there is always a part of the planet where it appears to be “morning,” with the star barely peaking over the horizon. Alternatively, there’s a part of the planet where it seems to be “evening,” where the star is again just barely peaking over the horizon, but it would appear to be setting. 

Typically, on Earth, we would think of the morning side as the star peaking over the eastern side, whereas the evening side would see the star setting into the western sky. However, exoplanets sometimes rotate in the opposite direction from planets in our solar system, so that mental model doesn’t always work for them.

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The JWST light curve for WASP-34b, clearly showing the dip in the star’s brightness as the planet passes in front of it.
Credit – NASA / ESA / CSA / R. Crawford (STScI)

It’s also important not to confuse the “morning” and “evening” sides with the “day” and “night” sides of the planet. On the day side, the full force of the star affects the planet, but on the night side, the star is never seen at all. The temperature differences on such a planet are massive, and cause much more extreme weather than anything we have experience with in our solar system.

That is the case for WASP-39b, one of the most studied exoplanets. It is a “hot Jupiter” and is roughly 1.3 times the size of the largest planet in our solar system, though it only masses in at about the same size as Saturn. It’s 700 light years away and is tidally locked to its star.

Exoplanet hunters have intently studied this exoplanet since its discovery in 2011. It was the target of JWST’s first exoplanet research when it began science operations. Since then, they’ve made several interesting discoveries, and the Nature paper describes a new one—that the “morning” side of WASP-39b is a few hundred degrees cooler than its “evening” side.

Fraser talks exoplanet atmosphere with expert Dr. Joanna Barstow.

This temperature discrepancy is likely due to atmospheric conditions on the planet itself. The paper’s authors believe there is an extremely strong wind on the planet that runs from day to night at thousands of miles an hour. The wind rotates from the day side through the evening side to the night side, then through the morning side back to the day side.

So, essentially, the morning side receives “air” that has been cooled while traveling through the planet’s night side. However, that air is still a blistering 600 C (1,150 F). The temperature on the evening side, though, is hotter at 800 C (1,450 F), much hotter than any conditions found on any planet in our solar system.

Detecting such a temperature difference on an exoplanet hundred of light years away is an impressive technical feat, and the study’s lead author, Néstor Espinoza, credits JWST’s capabilities for enabling it. The telescope watched the planet both while it was traversing in front of its star, but also while it was next to it and emitting its own, admittedly much fainter, light. 

JWST found methane in a different exoplanet atmosphere, as Fraser describes in this video.

They were differentiating between the starlight filtered through the atmosphere of the planet and when there was no filtered starlight coming through allowed the researchers to make temperature estimates. JWST is so sensitive they were also able to split the data into semi-circles to differentiate the”
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Review: Deuter Aircontact Ultra 50+5 and 45+5 SL Backpacks

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Ultralight Backpacks
Deuter Aircontact Ultra 50+5

$250, 55L/3,356 c.i., 2 lbs. 15 oz./1.33kg
Deuter Aircontact Ultra 45+5 SL

$250, 50L/3,051 c.i., 2 lbs. 11 oz./1.21kg

One adjustable size in both models

Aircontact Ultra 50+5: rei.com

Aircontact Ultra 45+5 SL: rei.com

To put Deuter’s updated-for-2024 Aircontact Ultra 50+5 ultralight backpack through the paces, I took it on a pair of quite rugged but also quite different backpacking trips this spring: a three-day hike through southern Utah’s Owl and Fish canyons with a max weight of about 30 pounds in the pack, and six days and about 60 miles backpacking the Grand Canyon’s Gems Route, repeatedly carrying extra water—and starting out with more than 40 pounds inside, including over 10 pounds of water and 11 pounds of food. As I expected, those trips revealed much about the Aircontact Ultra backpacks and why they might appeal to lightweight and ultralight backpackers.

First, I must acknowledge that 40 pounds significantly exceeds Deuter’s recommended max weight for these packs: I knew that but wanted to gauge the Aircontact Ultra’s comfort by exceeding its weight capacity and then seeing when it starts feeling comfortable as my pack weight decreased each day—as I sometimes do with packs in this weight class because, almost inevitably, many backpackers overload ultralight packs at the outset of a trip, or at various points during a long-distance hike, accepting a day or more of compromised comfort for the benefit of having a pack that’s lighter and will be adequately comfortable for most of the trip. I’ve done that countless times.

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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.

The Deuter Aircontact Ultra 50+5 harness.
” data-image-caption=”The Deuter Aircontact Ultra 50+5 harness.
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/07/11121334/Deuter-Aircontact-Ultra-505-harness.jpg?fit=200%2C300&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/07/11121334/Deuter-Aircontact-Ultra-505-harness.jpg?fit=683%2C1024&ssl=1″ tabindex=”0″ role=”button” src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/07/11121334/Deuter-Aircontact-Ultra-505-harness-683×1024.jpg?resize=683%2C1024&ssl=1″ alt=”The Deuter Aircontact Ultra 50+5 harness.” class=”wp-image-63988″ style=”aspect-ratio:0.6671875;width:488px;height:auto” srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/07/11121334/Deuter-Aircontact-Ultra-505-harness.jpg 683w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/07/11121334/Deuter-Aircontact-Ultra-505-harness.jpg 200w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/07/11121334/Deuter-Aircontact-Ultra-505-harness.jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/07/11121334/Deuter-Aircontact-Ultra-505-harness.jpg 150w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2024/07/11121334/Deuter-Aircontact-Ultra-505-harness.jpg 800w” sizes=”(max-width: 683px) 100vw, 683px” data-recalc-dims=”1″ />The Deuter Aircontact Ultra 50+5 harness.

In the Grand Canyon, having more than 40 pounds/18.1 kilos in the Aircontact Ultra 50+5 was certainly not “comfortable.” But nor was it all that bad. On that first day, we backpacked about six miles of rough dirt road just to reach the South Bass Trailhead, and then descended the often steep, loose, and rugged South Bass Trail for some 3,400 feet before
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How to Plan Food for a Backpacking Trip

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By Michael Lanza

You’re planning food for a backpacking trip—maybe for yourself or perhaps for your family or a small group of friends—and you have questions about how to do it. How much food do you need? What food should you bring? How complicated or simple do you want to make it? How do your food choices affect how much stove fuel you will need—or do you even need a stove? Drawing on decades of backpacking experience, this article will lay out some general guidelines and detailed advice that will help you plan food for all your backpacking trips.

Over the course of more than three decades and thousands of miles of backpacking all over the United States and around the world—including the 10 years I spent as Northwest Editor of Backpacker magazine and even longer running this blog—I have eaten countless meals in the backcountry and greatly refined my food planning over time.

Tet19 047 Me on Teton Crest Trail copy cropped 35
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 at a wilderness campsite off the Highline Trail in Wyoming’s Wind River Range.
” data-image-caption=”Our camp below Mount Oeneis and Sky Pilot Peak off the Highline Trail in the Wind River Range.
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/05/06224928/Wind8-031-Our-camp-below-Mount-Oeneis-and-Sky-Pilot-Peak-off-the-Highline-Trail-CDT-Wind-River-Range-WY..jpg?fit=300%2C200&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/05/06224928/Wind8-031-Our-camp-below-Mount-Oeneis-and-Sky-Pilot-Peak-off-the-Highline-Trail-CDT-Wind-River-Range-WY..jpg?fit=900%2C600&ssl=1″ tabindex=”0″ role=”button” src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/05/06224928/Wind8-031-Our-camp-below-Mount-Oeneis-and-Sky-Pilot-Peak-off-the-Highline-Trail-CDT-Wind-River-Range-WY.-1024×683.jpg?resize=900%2C600&ssl=1″ alt=”A backpacker at a wilderness campsite off the Highline Trail in Wyoming’s Wind River Range.” class=”wp-image-58509″ srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/05/06224928/Wind8-031-Our-camp-below-Mount-Oeneis-and-Sky-Pilot-Peak-off-the-Highline-Trail-CDT-Wind-River-Range-WY..jpg 1024w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/05/06224928/Wind8-031-Our-camp-below-Mount-Oeneis-and-Sky-Pilot-Peak-off-the-Highline-Trail-CDT-Wind-River-Range-WY..jpg 300w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/05/06224928/Wind8-031-Our-camp-below-Mount-Oeneis-and-Sky-Pilot-Peak-off-the-Highline-Trail-CDT-Wind-River-Range-WY..jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/05/06224928/Wind8-031-Our-camp-below-Mount-Oeneis-and-Sky-Pilot-Peak-off-the-Highline-Trail-CDT-Wind-River-Range-WY..jpg 150w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2023/05/06224928/Wind8-031-Our-camp-below-Mount-Oeneis-and-Sky-Pilot-Peak-off-the-Highline-Trail-CDT-Wind-River-Range-WY..jpg 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />Our camp below Mount Oeneis and Sky Pilot Peak off the Highline Trail in the Wind River Range.

I’ll offer this caveat in advance: I’m not someone who feels a great desire to eat “gourmet” style in the backcountry. I certainly want food that tastes good and is satisfying. If you’re not hiking far, it’s easier to carry a little more and spend time preparing special meals. I tend to hike all day, sometimes very long days, so I don’t want to spend much time in food
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