Like Earth, Mars experiences climatic variations during the course of a year because of the tilted nature of its orbit (aka. seasonal change). Similarly, these variations in temperature result in interaction between the atmosphere and the polar ice caps. On Earth, seasonal variations in temperature and precipitation cause the polar ice cap in one hemisphere to grow while the ice cap in the other hemisphere shrinks.
On Mars, however, things work a little differently. In addition to snow raining down on the polar ice caps during winter, the Martian polar ice caps also receive a great deal of frozen carbon dioxide (“dry ice”) in addition to snow. Recently, an international team of scientists used data from NASA’s Mars Global Surveyor (MGS) mission to measure how the planet’s polar ice caps grow and recede. Their results could provide new insights into how the Martian climate varies due to seasonal change.
The study that describes their findings was led by Haifeng Xiao, a research assistant with the Institute of Geodesy and Geoinformation Science at the Berlin Technical University. He was joined by researchers from Stanford University, the Université Paris-Saclay, the Institut Universitaire de France, and the German Aerospace Center’s (DLR) Institute of Planetary Research and Institute of Atmospheric Physics.
Time-lapse video showing seasonal changes around Mars’ South Pole. Credit: W.M. Calvin, et al. (2015)
What we know about the Martian polar ice caps indicates that they are composed of three parts. First, there is the Residual (or Permanent) Ice Cap, which consists of sheets of water ice several meters thick at the North Pole, and an 8-meter (~10 feet) thick sheet of frozen carbon dioxide at the South Pole. Beneath that are the Polar Layered Deposits (PLDs), which are 2 to 3 km (mi) thick and composed of water ice and dust.
Last is the Seasonal Ice Cap, a layer of frozen CO2 deposited on top of the permanent ice caps every winter. For the sake of their study, Haifeng and his colleagues focused on the Seasonal Ice Caps to reveal how they are affected by variations in seasonal temperatures and solar radiation – and how this is associated with annual variations in Mars’ climate. As Haifeng told Universe Today via email:
“Each Martian year, approximately 30% of the atmosphere’s CO2 mass is in vivid exchange with the polar surfaces through the seasonal deposition/sublimation. Temporal variations of levels and volumes of snow/ice associated with this process can put crucial constraints on the Mars climate system and volatile circulation models.
“In addition, the seasonal accumulation of the CO2 ice to form these seasonal polar caps can be affected by dust storms, cold spots, katabatic and orographic winds, and local shadowing. Thus, short and long-term variabilities of the seasonal polar caps could also indicate the variabilities of the Mars climate.”
During a Martian year, which lasts over 687 Earth days (or 668.5 Sols), seasonal changes lead to atmospheric carbon dioxide migrating from the North Pole to the South Pole (and vise versa). These seasonal actions are responsible for transporting large amounts of dust and water vapor, which leads to frosts and the formation of large cirrus clouds visible from space.
This image from the Mars Reconnaissance Orbiter (MRO) shows the “spiders” emerging from the carbon dioxide ice cap at the South Pole of Mars. Credit: NASA/JPL-Caltech
This process of sublimation and exchange between the poles is also responsible for notable geological features on Mars, such as the araneiform terrain (aka. “spiders”) near the South Pole and the way the dune fields in the northern planes become furrowed with the arrival of seasonals. As Haifeng explained, understanding the relationship between the seasonal polar caps and the formation of geological features on Mars could lead to a better understanding of the Martian environment.
Over the past two decades, measurements of the polar ice caps have been conducted using various methods – gravity variation, neutron, and gamma-ray flux – and modeled based on General Circulation and Energy
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Astronomers Discover a New Meteor Shower. The Source is Comet 46P/Wirtanen
Like many of you, I love a good meteor shower. I have fond memories of the Leonid meteor storm back in 1999 when several hundred per hour were seen at peak. Sadly meteor storms are not that common unlike meteor showers of which, there are about 20 major showers per year. Wait, there’s another one and this time it comes from the debris left behind from Comet 46P/Wirtanen with an expected peak on December 12. Last year, 23 meteors were seen on that night that matched the location of the comets trail.
Comets (and some asteroids) leave a trail of debris behind them like a trail of celestial breadcrumbs. If the orbit of a comet crosses the orbit of the Earth then the particles from the debris (that are often no larger than grains of sand) collide with our atmosphere. At the immense speeds (of the order of 60 km per second, the particles falling through the atmosphere cause the gas to glow giving rise to the classic shooting star we see in the sky. Because the orbits of Earth and comets are relatively fixed, this process repeats itself every time we go through the same part of the orbit giving us the familiar annual meteor showers.
One such comet that it seems may become host to a new annual shower is Comet 46P/Wirtanen (46P). It nearly hit the headlines previously when it had been initially selected as the target for the Rosetta mission which, as you may recall, visited 67P/Churyumov-Gerasimenko instead. 46P is known as a short period comet taking 5.4 years to complete one orbit of the Sun. It is among the family of comets known as a Jupiter comet which has a most distant point from the Sun of between 5 and 6 astronomical units (1 AU is the average distance between the Sun and Earth). Observations have suggested it has a diameter of about 1.4km.
Comet 67P/Churyumov-Gerasimenko from Rosetta mission (Credit – NASA)
Due to the high levels of ice present in comets, it’s not unusual for active areas on their surface to appear as the ices sublimate into gasses or pockets of gas escape. Observations using the TRAPPIST telescope (The Transiting Planets and Planetesimals Small Telescope) suggest 40% of the surface is active which is higher than the usual 5-10% for Jupiter family comets. A recent study found the presence of mm sized dust particles in the comet’s coma which should be visible upon entering Earth’s atmosphere.
The orbit of 46P has a very low minimum orbit intersection distance (MOID) to Earth of just 0.071AU. The MOID between two objects that orbit a common point is the distance between the closest points of their orbits. The low MOID and the mm sized particles mean there is a high liklihood it could be the source of a meteor shower. Previous observations however have revealed no positive confirmation of peaks in 2017 and 2019.
During the 2017 and 2019 predictions, it seems the low velocity of the particles coupled with the radiant (the point of apparent origin of the shower) below the horizon suggest that visibility may have been severely limited. The radiant of this predicted shower is in the constellation Sculptor and the shower has been dubbed the Lambda Sculptorids.
The prediction for the 2023 shower, which predicted an encounter from a stream of debris from an outburst in 1974, suggested an outburst of meteors on December 12 between 12:08 and 20:06. A further outburst was predicted between 17:05 and 06:26 on December 13. The team who presented their findings in Astronomy and Astrophysics reported meteor activity as predicted and detected 23 meteors from the new shower on the night of December 12 2023. The team are now looking at the models to see what we might expect to see this year and whether Lamba Sculptorids need to be added to our list of annual meteor showers.
Source : Observations of the new meteor shower from comet 46P/Wirtanen
The post Astronomers Discover a New Meteor Shower. The Source is Comet 46P/Wirtanen appeared first on Universe Today.
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The 12 Best Dayhikes in Yosemite
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.
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.
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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
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 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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