Buzz
We often become so engrossed in the hunt for alien life on exoplanets that we forget the countless puzzles still to be solved in our own solar system. Thankfully, scientists continue their quest to uncover answers in our corner of the cosmos.
10. The Enigmatic Heat of the Sun's Corona
As we’ve explored previously, scientists have long been puzzled by the extreme temperature difference between the Sun’s corona, or outer atmosphere, and its photosphere, or visible surface. Logically, the Sun's surface is about 6,000 Kelvin (around 6,000 degrees Celsius or 10,000 °F), while the corona can reach temperatures up to 300 times hotter. “That’s a bit of a puzzle,” said Jeff Brosius, a space scientist at NASA’s Goddard Space Flight Center in Maryland. “Typically, things cool down the farther you move from a heat source. When you roast a marshmallow, you move it closer to the fire, not farther away.”
Recent findings provide strong evidence that nanoflares—and the energetic particles they generate—are likely a key contributor to the additional heat. Although nanoflares are miniature versions of solar flares (which can heat solar plasma to tens of millions of degrees in just seconds), they still release quick, small bursts of heat and energy almost continuously. While we cannot yet observe them directly, this may change with NASA’s NuSTAR space telescope, which will capture high-energy X-ray images of them. However, scientists need to wait for the Sun to calm down, as its active state may obscure the nanoflares' activity.
In the meantime, the Interface Region Imaging Spectrograph (IRIS) offers the best method to detect nanoflares indirectly by observing coronal loop footpoints. A coronal loop is a hot plasma arc extending from the Sun’s surface into the corona, glowing brightly in ultraviolet and X-rays. A footpoint is the point where magnetic loops intersect the Sun’s surface. While IRIS cannot directly observe the coronal heating events, it can detect the rapid, small brightening at the coronal loop footpoints that indicate their presence.
While other theories have been ruled out, mounting evidence supports nanoflares as the solution to the coronal heating conundrum. If this theory holds true, NuSTAR should detect at least one nanoflare every few minutes. If no nanoflares are observed, scientists will have to reconsider the hypothesis.
9. The Mystery Behind the Dark Material on Protoplanet Vesta
Rocks provide crucial insights into a protoplanet’s history since they form under very specific conditions. NASA’s Dawn spacecraft recently revealed details about the mysterious dark material scattered across Vesta’s surface. This substance absorbs light similarly to soot, but scientists have been eager to uncover its composition and origins. Understanding this could offer valuable clues as to why Vesta began its journey toward becoming a planet over four billion years ago but never fully evolved past being a protoplanet.
For over a year, scientists have known that the dark material contained high levels of carbon. However, they recently discovered that serpentine, a silicate mineral that forms rocks, is also part of this dark material. Serpentine earned its name due to its resemblance to snakeskin.
The discovery of serpentine helps unravel some of Vesta’s formation mystery. Since serpentine would be destroyed by temperatures above 400 degrees Celsius (700 °F), the dark material must not have been exposed to extreme heat. We already know that Vesta was once very hot, so this dark material couldn't have originated from Vesta itself.
This leaves the most plausible explanation as a relatively slow impact from a carbon-rich asteroid. Had the impact been too fast, the intense heat would have destroyed the serpentine. Additionally, the way the dark material is dispersed across Vesta's surface matches the pattern expected from a low-speed asteroid impact.
8. The Enigma of Venus’s Atmosphere
“This all began with a mystery back in 1978,” explained Glyn Collinson from NASA’s Goddard Space Flight Center in Maryland. “When the Pioneer Venus Orbiter entered orbit around Venus, it detected something very strange—a hole in the planet’s ionosphere. This was a region where the density simply dropped off, and we hadn’t seen anything like it for 30 years.”
The ionosphere is an electrically charged layer of Venus’s atmosphere. When the European Space Agency’s Venus Express started orbiting Venus, it was positioned much higher than its predecessor. Even from this higher orbit, Venus Express observed the same holes. This suggested that these holes extended deeper into the atmosphere than originally thought. Furthermore, the Pioneer Venus Orbiter detected these holes during the solar maximum, a period of peak solar activity. In contrast, Venus Express observed the holes during the solar minimum, indicating that these holes are more widespread than previously realized.
To understand the situation on Venus, it's important to know that the side of its ionosphere facing the Sun is constantly bombarded by solar wind, a flow of charged particles from the Sun. The ionosphere serves as a thin shield that wraps around Venus, extending from the planet's front and trailing off like the tail of a comet. You can think of the ionosphere as the air streaming around a golf ball in flight.
When the solar wind strikes the ionosphere, the plasma accumulates, creating a thin magnetosphere around the planet. A magnetosphere is a region around a planet where its magnetic field can deflect solar wind.
Venus Express is capable of measuring the weak magnetic field surrounding Venus. However, it suggested that there were not two holes behind the planet. Instead, scientists now believe there are two long, wide cylinders extending from Venus's surface into outer space. It’s possible that charged particles are being squeezed out of these cylinders like toothpaste from a tube.
This leads to another intriguing mystery. What allows these magnetic fields to penetrate the ionosphere, reach the planet’s surface, and potentially even enter the planet? While we've uncovered one mystery of Venus, we’ve stumbled upon another.
7. The Theta Aurora
Auroras, the spectacular light displays commonly known as the Northern or Southern Lights, typically form when the solar wind interacts with the Earth’s magnetic field, also called the magnetosphere. Essentially, they provide a visible demonstration of the Sun’s influence on our planet.
Theta auroras tend to occur at higher latitudes, closer to the poles, compared to typical auroras. These unique auroras can only be observed from above, where their shape resembles the Greek letter theta (θ).
The creation of an aurora depends on how the interplanetary magnetic field, carried by the solar wind, aligns with the Earth’s magnetic field. When these two fields intersect, Earth’s magnetic field will point north. However, if the interplanetary field points south, the magnetic field lines will be directed oppositely. This sets off a process known as magnetic reconnection (still not fully understood), which realigns the magnetic field lines in a new configuration.
This new alignment enables solar wind particles to enter Earth’s magnetosphere, a vast magnetic bubble surrounding our planet. As these solar particles follow the planet’s magnetic field lines and collide with atoms in the upper atmosphere, an aurora forms. Typically, this occurs at latitudes between 65 and 70 degrees north or south of the equator.
However, theta auroras can form at even higher latitudes if the interplanetary magnetic field is pointing north instead of south. Scientists recently discovered that when this happens, magnetic reconnection can trap plasma (ionized gas) within the magnetosphere. The trapped plasma heats up, potentially giving rise to a theta aurora.
6. The Mystery of Titan’s Sand Dunes
Titan, Saturn’s largest moon, is the only moon known to have a dense atmosphere. Its lakes and seas are made of methane and ethane. This unique moon also features massive, wind-swept dunes that stretch for hundreds of miles, are over a mile wide, and rise hundreds of yards high.
Initially, the presence of dunes seemed perplexing because it was thought that Titan’s surface only experienced gentle breezes. However, subsequent studies suggested that the winds must be stronger than previously thought. NASA’s Cassini spacecraft also captured images of the particles responsible for forming these dunes.
“It was unexpected that Titan had particles the size of grains of sand—we still don’t fully understand where they come from—and that it had winds powerful enough to move them,” said Devon Burr from the University of Tennessee. “Before seeing the images, we believed the winds were likely too mild to create this movement.”
The most intriguing mystery for scientists was the shape of the dunes. Cassini’s data indicated that the winds on Titan generally blew from east to west. However, the dunes around craters and mountains appeared to have formed in the opposite direction.
In a NASA high-pressure wind tunnel, Burr and her team spent six years simulating the wind and sand conditions found on Titan. Ultimately, they discovered that the winds had to blow at least 50% faster than previously thought in order to create the dunes. Titan’s thick atmosphere made these higher wind speeds necessary.
Their findings also provided an explanation for the unique shape of the dunes. According to their model, Titan’s winds are typically light, blowing from east to west, and cannot form dunes. However, twice every Saturn year, which equals 30 Earth years, the winds shift direction and blow faster when the Sun crosses Titan’s equator. Burr believes these rapid wind shifts are responsible for the formation of the dunes and their unusual shape. Cassini might have missed these high wind speeds because they occur so infrequently.
5. The Surprising Volcanoes of Mercury
NASA’s MESSENGER spacecraft has uncovered surprising details about Mercury’s early planetary history. Initially, scientists assumed that Mercury lacked the volatile compounds needed to produce volcanic eruptions, leading to the belief that the planet had never experienced active volcanoes. However, MESSENGER’s photos forced researchers to reconsider their assumptions.
MESSENGER’s images revealed pyroclastic ash deposits, which are created from rock fragments ejected by volcanic vents. This discovery confirmed that Mercury indeed had volatile compounds. The photos also suggested that volcanic eruptions occurred over a long stretch of Mercury’s history.
This raised another question: Did the volatile compounds inside Mercury’s core explode early in its history, or did these eruptions happen over a much longer period of time?
A team of researchers from Brown University argues that the volcanic activity spanned a considerable period. Their evidence came from examining the vents of the volcanoes. If all the eruptions had occurred at once, the vents would have shown similar levels of degradation. However, the scientists observed varying degrees of wear, supporting the theory of eruptions over an extended time frame.
By assessing the extent of degradation, the team estimated that Mercury’s volcanic activity likely took place between 1 to billion years ago. While this might sound ancient, it is still considered geologically young. Had all the eruptions happened near Mercury’s formation, the craters would have been about 4.5 billion years old.
This discovery also sheds light on the formation of Mercury. Two main theories previously suggested that Mercury was once larger but lost its outer layers either due to intense solar heat or a significant impact shortly after the planet’s formation. However, given the new insights into volatile compounds, both theories seem unlikely.
4. Mars’s Climate History
Black Beauty, a Mars meteorite discovered in 2011 in the Sahara Desert, may hold vital clues about Mars’s climate history. This glossy, dark rock contains zircons, tough minerals formed when lava cools, capable of withstanding almost any chemical attack. These zircons can help determine the age of rocks and provide insight into a planet’s climate. Florida State Professor Munir Humayun remarked, “When you find a zircon, it’s like finding a watch. A zircon begins keeping track of time from the moment it’s born.”
Humayun and his team were taken aback to find that some of the zircons in Black Beauty were formed 4.4 billion years ago, a time when Mars was a young planet, possibly with an environment that could have supported life.
By analyzing variations in the oxygen atoms found within these zircons, Humayun was able to piece together Mars’s climate history, much like an archaeologist reconstructing human history from ancient artifacts and skeletal remains. The zircons serve as a record, preserving the planet's history of water vapor and climate change.
Humayun uncovered that Mars had abundant water around 4.5 billion years ago, but a major transformation took place after that. The dry, desert-like environment of Mars, which we see today, has persisted for at least 1.7 billion years. This raises a compelling question: Could Mars have once supported life, given its past water-rich environment?
For ongoing climate research, scientists are studying dust devils on Mars. As we've discussed, dust devils resemble dusty tornadoes, but the comparison to Earth weather ends there. “The Martian air is so thin, dust has a much greater impact on energy transfers in the [Mars] atmosphere and on the surface than it does in Earth’s dense atmosphere,” explained Udaysankar Nair from the University of Alabama.
During the day, dust particles in the Martian air can block sunlight, preventing the surface from warming. At night, this same dust releases long-wave radiation that heats the surface. A deeper understanding of the dust and dust devils could offer us valuable insights into the Martian climate.
3. Organics On Mars
NASA's Curiosity rover not only detected methane spikes, but also uncovered organic molecules inside rock samples. The powder extracted from a rock known as Cumberland marks the first confirmed discovery of organics on Mars's surface. However, it's still uncertain whether these organics originated on Mars itself or were brought by carbon-rich meteorites.
While NASA scientists didn’t find organics in materials exposed on the Martian surface, this is understandable due to the destructive nature of cosmic radiation and perchlorates, which contain chlorine that alters molecules and gradually degrades surface organics over time.
Organic molecules are composed of carbon bonded with elements such as hydrogen. These molecules are vital for life as we understand it, but their mere presence doesn't imply life. We haven’t confirmed if Mars ever hosted living organisms, but this discovery indicates that ancient Mars possessed conditions conducive to supporting some forms of life.
Scientists had identified three essential components for life on Mars: water, an energy source, and organics. With the discovery of organics, they now possess the complete list of necessary ingredients for life, whether it existed in the past or still exists today.
The Cumberland rock samples provided valuable insights into the planet’s water loss. By analyzing the ratio of deuterium to hydrogen in the rock and comparing it to the water vapor in the atmosphere, scientists concluded that much of Mars’s water loss occurred after the formation of the rock. However, their findings also suggested that a significant portion of the planet’s original water had been lost even before Cumberland came into existence.
2. Plasma Rainstorms On The Sun
The Sun experiences rainstorms with high winds that bear a striking resemblance to storms on Earth. However, instead of water, the Sun’s rain consists of plasma—ionized gas that falls from the corona to the surface at an astounding speed of 200,000 kilometers (125,000 miles) per hour. The corona is the Sun’s outermost layer, and when it rains from there, the droplets are enormous—each one as large as Ireland, and thousands of these droplets fall in a single coronal rain shower.
Plasma rain has been known to scientists for about 40 years, but it wasn’t until they received detailed data from modern satellites and observatories that they could finally begin to explain its occurrence.
This is where the similarities to Earth’s weather become most evident. Under specific conditions, the Sun’s dense, hot plasma clouds will cool and condense, eventually falling to the surface as coronal raindrops.
A process of rapid evaporation also contributes to the formation of clouds. However, on the Sun, it is the intense explosions of solar flares that drive this evaporation. Telescopic images show that solar flares, bursts of radiation from the Sun’s surface, precede solar rainstorms. Scientists believe that a sudden and sharp temperature drop causes the coronal gas to transform into solar raindrops.
1. Zebra Stripes In Van Allen Radiation Belt
Earth is enveloped by two Van Allen radiation belts: an inner and an outer one, both shaped like doughnuts and filled with high-energy electrons and protons. However, in early 2014, scientists revealed that NASA’s twin Van Allen Probes had detected an unusual, persistent zebra stripe pattern in the high-energy electrons within the inner radiation belt.
Earth’s magnetic field keeps these radiation belts in place. Yet, Earth itself didn’t seem like the most likely cause of the zebra stripes. Initially, most scientists thought that heightened solar wind would create such a pattern. But that hypothesis was ruled out when the stripes persisted despite low solar wind activity.
In the end, scientists discovered the answer they had previously thought improbable. It turns out that Earth’s rotation is responsible for the zebra stripes. The tilt in our planet’s magnetic field axis causes Earth’s rotation to generate a weak, oscillating electric field that impacts the entire inner radiation belt. Imagine the electrons in the radiation belt as pieces of taffy; the oscillations act like a candy machine, stretching and folding the taffy, which results in the striped pattern in the inner radiation belt.
