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Extrasolar planets are being discovered at a rapid rate, with 4,531 planets in 3,363 systems (with another 7,798 candidates awaiting confirmation). Of these, 166 have been identified as rocky planets (aka. “Earth-like”) while another 1,389 have been rocky planets that are several times the size of Earth (“Super-Earths). As more and more discoveries are made, the focus is shifting from the discovery process towards characterization.

In order to place tighter constraints on whether any of these exoplanets are habitable, astronomers and astrobiologists are looking for ways to detect biomarkers and other signs of biological processes. According to a new study, astronomers and astrobiologists should be on the lookout for indications of a carbon-silicate cycle. On Earth, this cycle ensures that our climate remains stable over the course of eons and could be the key to finding life on other planets.

The study, titled “Carbon cycling and habitability of massive Earth-like exoplanets,” was conducted by Amanda Kruijver, Dennis Honing, and Wim van Westrenen – three Earth scientists with the Vrije Universiteit Amsterdam. Honing is also a fellow with the Origins Center, a Netherlands-based national science institute committed to researching the origins and evolution of life in our Universe. Their study is currently being reviewed for publication in The Planetary Science Journal.

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Diagram of the fast carbon cycle, showing the movement of carbon between land, atmosphere, and oceans. Credit: U.S. DOE/BERIS

On Earth, this two-step cycle ensures that carbon dioxide (CO2) levels in our atmosphere remain relatively consistent over time. This first step consists of carbon dioxide being removed from our atmosphere by reacting with water vapor to form carbonic acid, which weathers and dissolves silicate rock. The products of this weathering are washed into the oceans (forming carbonate rock), which sink to the seafloor and become part of the Earth’s mantle.

This is where the second step comes into play. Once in the mantle, carbonate rocks are melted down to create silicate magma and CO2 gas, the latter of which is released back into the atmosphere through volcanic eruptions. As Dr. Honing explained to Universe Today via email, the process is also affected by changes in surface conditions:

“Importantly, the speed of this process depends on the surface temperature: If the surface gets hotter, weathering reactions speed up, and more CO2 can be removed from the atmosphere. Since CO2 is a greenhouse gas, this cools mechanism down the surface, so we have a stabilizing feedback. We have to point out that this stabilizing feedback needs a long time to be efficient, in the order of hundreds of thousand years or even millions of years.”

A key consideration here is how the Sun has been getting hotter with time, Dr. Honing added. Compared to Earth’s early history, our planet now receives roughly 30% more energy from the Sun, which is why atmospheric CO2 levels were higher in the distant past. Therefore, it is safe to say that weathering becomes more pronounced as a planet gets older and that atmospheric CO2 levels will drop at an increasing rate at this point in their evolution.

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The terrestrial planets of our Solar System at approximately relative sizes (left to right): Mercury, Venus, Earth, and Mars. Credit: LPI

Since this is a simple chemical process, there is no reason to think that a carbon-silicate cycle couldn’t function on other planets – provided they have liquid water on their surfaces. For exoplanet researchers and astrobiologists, the presence of liquid water has been a key biosignature in the ongoing search for extraterrestrial life. The issue of plate tectonics has also been raised since this plays a significant role in maintaining Earth’s habitability over time. Said Dr. Honing:

“In our

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The 12 Best Dayhikes in Yosemite

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By Michael Lanza

The natural beauty, variety, pristine quality, and scale of America’s National Park System have no parallel in the world. Still, a handful of flagship parks rise above the rest—including, unquestionably, Yosemite. Created in 1890, our third national park harbors some of the most breathtaking and inspiring wild lands in the entire parks system. And you can reach much of Yosemite’s finest scenery on dayhikes.

This story shares my picks for the 12 best dayhikes in Yosemite, from popular hikes like Half Dome, the Mist Trail, and Upper Yosemite Falls to some trails and peaks you may not have heard of—including the nearly 11,000-foot summit known to have “the best 360 in Yosemite.”

This list of Yosemite’s best hikes is drawn from my numerous trips dayhiking and backpacking all over the park going back more than 30 years, including the 10 years I spent as a field editor for Backpacker magazine and even longer running this blog. Use this story as your guide and you will see the best scenery in Yosemite that’s accessible on a moderate to full day of hiking.

Please share your thoughts on any of these hikes or your own favorites in Yosemite in the comments section at the bottom of this story. I try to respond to all comments.

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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.

May Lake in Yosemite National Park.
” data-image-caption=”May Lake in Yosemite National Park.
” data-medium-file=”″ data-large-file=”″ src=”″ alt=”May Lake in Yosemite National Park.” class=”wp-image-38065″ srcset=” 1024w, 300w, 768w, 1080w, 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />May Lake in Yosemite National Park. Click photo for my e-guide “The Prettiest, Uncrowded Backpacking Trip in Yosemite.”

May Lake and Mount Hoffmann

2.4 to 6 miles, 500 to 2,100 feet up and down

From the 10,850-foot summit of Mount Hoffmann (lead photo at top of story) in the geographic center of Yosemite—often described as having “the best 360 in Yosemite”—you’ll look out over virtually the entire park, seeing Half Dome, Clouds Rest, and Yosemite Valley, the Clark and Cathedral Ranges, and the sea of peaks sprawling across northern Yosemite. The hike culminates with a steep, third-class scramble up the final 200 feet to the summit, where you stand at the brink of cliffs with serious exposure (although you don’t have to stand at that dizzying edge).

The summit of Yosemite’s Mount Hoffmann.
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The Kuiper Belt is Much Bigger Than We Thought

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NASA’s New Horizons spacecraft is just over 8.8 billion km away, exploring the Kuiper Belt. This icy belt surrounds the Sun but it seems to have a surprise up its sleeve. It was expected that New Horizons would be leaving the region by now but it seems that it has detected elevated levels of dust that are thought to be from micrometeorite impacts within the belt. It suggests perhaps that the Kuiper Belt may stretch further from the Sun than we thought! 

The Kuiper Belt is found beyond the orbit of Neptune and is thought to extend out to around 8 billion km. Its existence was first proposed in the mid-20th century by Gerard Kuiper after whom the belt has been named. It’s home to numerous icy bodies and dwarf planets and offers valuable insight into the formation and evolution of the Solar System.

Launched by NASA in January 2006 atop an Atlas V rocket, the New Horizon’s spacecraft embarked on its mission to explore the outer Solar System. The primary objective was to perform a close flyby of Pluto, which it did 9.5 years after it launched, and continue on to explore the Kuiper Belt.

New Horizons completed its flyby of Pluto in 2015, and has been travelling through the Kuiper Belt since. As it travels through the outer reachers of the region, almost 60 times the distance from Earth to the Sun, its Venetia Burney Student Dust Counter (SDC) has been counting dust levels. The instrument was constructed by students at the Laboratory for Atmospheric Space Physics at the University of Colorado Boulder. Throughout New Horizon’s journey, SDC has been monitoring dust levels giving fabulous insight into collision rates among objects in the outer Solar System. 

The New Horizons instrument payload that is currently doing planetary science, heliospheric measurements, and astrophysical observations. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
The New Horizons instrument payload that is currently doing planetary science, heliospheric measurements, and astrophysical observations. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The dust particle detections announced in a recent paper published in the Astrophysical Journal Letters by lead author Alex Doner are thought to be frozen remains from collisions between larger Kuiper Belt Objects (KBOs). The results were a real surprise and challenged the existing models that predicted a decline in dust density and KBO population. It seems that the belt extends many billions of miles beyond the current estimates or maybe even that there is a second belt!

The results came from data gathered over a three year period during New Horizon’s journey from 45 to 55 astronomical units (where 1 astronomical unit is the average distance between the Sun and Earth). While New Horizon’s was gathering data about dust, observatories such as the 8.2-meter optical-infrared Subaru Telescope in Hawaii have been making discoveries of new KBOs. Together these findings suggest the Kuiper Belt objects and dust may well extend a further 30 AUs out to about 80 AUs from the Sun.

New Horizons is now in its extended mission and hopefully has sufficient power and propellant to continue well into the 2040s. At its current velocity that will take the spacecraft out to about 100 AU from the Sun so the research team speculate that the SDC could identify the transition point into interstellar space.

Source : NASA’s New Horizons Detects Dusty Hints of Extended Kuiper Belt

The post The Kuiper Belt is Much Bigger Than We Thought appeared first on Universe Today.

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A Planetary Disk in the Orion Nebula is Destroying and Replenishing Oceans of Water Every Month

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Planet-forming disks are places of chaotic activity. Not only do planetesimals slam together to form larger worlds, but it now appears that the process involves the destructive recycling of water within a disk. That’s the conclusion from scientists studying JWST data from a planetary birth crèche called d203-506 in the Orion Nebula.

The data they studied suggest that an amount of water equivalent to all of Earth’s oceans is created and replenished in a relatively short period—about a month. According to study co-lead Els Peeters at Western University in Canada, it was relatively easy to discover this process in the protoplanetary disk. “This discovery was based on a tiny fraction of our spectroscopic data,” she said. “It is exciting that we have so much more data to mine and I can’t wait to see what else we can find.”

The Orion Nebula is a vast active star- and planet-forming region and the d203-506 protoplanetary disk lies within it at a distance of about 1,350 light-years away from Earth. Astronomers study the nebula to understand all aspects of star birth since there are so many newborn stars there. In addition, many are surrounded by disks of gas and dust, called protoplanetary disks (proplyds, for short). Those regions are excellent places to observe planet-formation processes, and particularly the interplay between the young stars and their disks.

The Orion Nebula, one of the most studied objects in the sky. It's likely that many of its protostars and their planetary disks contain water in some form. Image: NASA
The Orion Nebula is one of the most studied objects in the sky. Many of its protostars and their planetary disks likely contain water in some form. Image: NASA

The Water Cycle of a Proplyd

We all know that water is an important ingredient for life. It certainly played a role in creating and sustaining life on our planet. As it turns out, water is a significant fraction of the materials in a proplyd. In the infant Solar System, water existed throughout our proplyd long before any of the planets formed, largely in their icy form, either as icy bodies or locked into asteroids and planetesimals. It also exists in interstellar space.

This view of Earth’s horizon was taken by an Expedition 7 crewmember onboard the International Space Station, using a wide-angle lens while the Station was over the Pacific Ocean. A new study suggests that Earth's water didn't all come from comets, but likely also came from water-rich planetesimals.  Credit: NASA
This view of Earth’s horizon by an Expedition 7 crewmember onboard the International Space Station. A new study suggests that Earth’s water didn’t all come from comets, but likely also came from water-rich planetesimals. Credit: NASA

Most of Earth’s water got delivered to the forming planet over millions of years. It melted or outgassed to form the oceans, rivers, and lakes we see today. But, some fraction of the water in our system’s birth disk probably went through a “freeze-thaw” cycle within the disk. That happened when the Solar System was still just a disk of gas and dust. The water was essentially destroyed and then re-formed at higher temperatures.

We can’t see that effect anymore in our system. But, astronomers can point telescopes at other proplyds to see if the same process happens there. That’s what Peeters and her team did. They used JWST to look at d203-506. There, bright young stars flood the nearby regions in the proplyd with intense ultraviolet radiation. The UV breaks up water molecules to form hydroxyl molecules and that process also releases infrared light. JWST can search out that light and report back on how much hydroxyl
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