A team of researchers in Japan has discovered a gigantic streak structure in the cloud tops of Venus. The discovery is based on observations of Venus by the Japanese spacecraft Akatsuki. The findings were published in January 9th in the journal Nature Communications.
Venus is unlike any other planet in the Solar System. The entire planet is shrouded in thick clouds of sulfuric acid between altitudes of 45 km to 70 km. This thick shroud has prevented scientists from studying Earth’s so-called “sister planet” in detail. But Japanese researchers are making progress.
A handful of spacecraft have used ion engines to reach their destinations, but none have been as powerful as the engines on the BepiColombo spacecraft. BepiColombo is a joint mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA.) It was launched on October 20, 2018, and has gone through weeks of in-flight commissioning. On Sunday it turned on its powerful ion thrusters for the first time.
“We put our trust in the thrusters and they have not let us down.” – Günther Hasinger, ESA Director of Science.
The architectural design behind Japan’s new space research center is mind-boggling. The futuristic building will incorporate elements of spacecraft design, which emphasize light weight and high functionality. The whole thing will be suspended over a man-made, Moon-like crater.
Having studies countless asteroids in near-Earth space, astronomers have come to understand that the majority of these rocks fall into one of two categories: S-type (grey) and C-type (red). These are defined by the types of materials on their surfaces, with S-type asteroids being primarily composed of silicate rock and C-type asteroids being made up of carbon materials.
However, there is also what are known as blue asteroids, which make up only a fraction of all known Near-Earth Objects (NEO). But when an international team astronomers observed the blue asteroid (3200) Phaeton during a flyby of Earth, they spotted behavior that was more consistent with a blue comet. If true, then Phaeton is of a class of objects that are so rare, they are almost unheard of.
Earlier this week asteroid Ryugu had a visitor. The Mobile Asteroid Surface Scout (MASCOT) landed on Ryugu on October 3rd after it was successfully deployed from the Japanese Hayabusa2 space probe. The little hopping robot’s visit was brief however, and it stopped functioning on Oct. 4th.
Ever since astronauts began going to space for extended periods of time, it has been known that long-term exposure to zero-gravity or microgravity comes with its share of health effects. These include muscle atrophy and loss of bone density, but also extend to other areas of the body leading to diminished organ function, circulation, and even genetic changes.
For this reason, numerous studies have been conducted aboard the International Space Station (ISS) to determine the extent of these effects, and what strategies can be used to mitigate them. According to a new study which recently appeared in the International Journal of Molecular Sciences, a team of NASA and JAXA-funded researchers showed how artificial gravity should be a key component of any future long-term plans in space.
Within Earth’s orbit, there are an estimated eighteen-thousands Near-Earth Asteroids (NEAs), objects whose orbit periodically takes them close to Earth. Because these asteroids sometimes make close flybys to Earth – and have collided with Earth in the past – they are naturally seen as a potential hazard. For this reason, scientists are dedicated to tracking NEAs, as well as studying their origin and evolution.
On October 5th, 2017, Vice President Mike Pence announced the Trump administration’s plan to return astronauts to the Moon. Looking to the long-term, NASA and several other space agencies are also intent on establishing a permanent lunar base there. This base will not only provide opportunities for lunar science, but will facilitate missions to Mars and beyond.
The only question is, where should such a base be built? For many years, NASA, the ESA and other agencies have been exploring the possibility of stable lava tubes as a potential site. According to new study by a team of international scientists, the presence of such a tube has now been confirmed in the Marius Hills region. This location is likely to be the site of future lunar missions, and could even be the site of a future lunar habitat.
In 2009, data provided by the Terrain Camera aboard JAXA’s SELENE spacecraft indicated the presence of three huge pits on the Moon. These pits (aka. “skylights”) were of particular interest since they were seen as possible openings to subsurface lava channels. Since then, the Marius Hills region (where they were found) has been a focal point for astronomers and planetary scientists hoping to confirm the existence of lava tubes.
Together, they examined data from the SELENE mission’s Lunar Radar Sounder (LRS) from locations that were close to the Marius Hills Hole (MHH) to determine if the region hosted stable lava tubes. Such tubes are a remnant from the Moon’s past, when it was still volcanically active. These underground channels are believed to be an ideal location for a lunar colony, and for several reasons.
For starters, their thick roofs would provide natural shielding from solar radiation, cosmic rays, meteoric impacts, and the Moon’s extremes in temperature. These tubes, once enclosed, could also be pressurized to create a breathable environment. As such, finding an entrance to a stable lava tube would the first step towards selecting a possible site for such a colony.
As Junichi Haruyama, a senior researcher at JAXA and one of the co-authors on the study, explained in a University of Purdue press release:
“It’s important to know where and how big lunar lava tubes are if we’re ever going to construct a lunar base. But knowing these things is also important for basic science. We might get new types of rock samples, heat flow data and lunar quake observation data.”
Granted, the LRS was not specifically designed to detect lava tubes, but to characterize the origins of the Moon and its geologic evolution. For this reason, it did not fly close enough to the Moon to obtain extremely accurate information on the subsurface. Nevertheless, as SELENE passed near the Marius Hills Hole, the instrument picked up a distinctive echo pattern.
This pattern was characterized by a decrease in echo power followed by a large second echo peak. These two echoes correspond to radar reflections from the Moon’s surface, as well as the floor and ceiling of the open lava tube. When they analyzed this pattern, the research team interpreted it is evidence of a tube. They found similar echo patterns at several locations around the hole, which could indicate that there is more than one lava tube in the region.
To confirm their findings, the team also consulted data from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission. Consisting of two spacecraft, this collaborative effort collected high-quality data on the Moon’s gravitational field between 2011 and 2012. By using GRAIL data that identified mass deficits under the surface, which are evidence of caverns, the team was able to narrow down their search.
Jay Melosh, a GRAIL co-investigator and Distinguished Professor of Earth, Atmospheric and Planetary Sciences at Purdue University, was also a co-author on the paper. As he explained:
“They knew about the skylight in the Marius Hills, but they didn’t have any idea how far that underground cavity might have gone. Our group at Purdue used the gravity data over that area to infer that the opening was part of a larger system. By using this complimentary technique of radar, they were able to figure out how deep and high the cavities are.”
On Earth, stable lava tubes have been found that can extend for dozens of kilometers. To date, the longest and deepest to be discovered is the Kazumura Cave in Hawaii, which is over a kilometer (3,614 feet) deep and 65.5 km (40.7 mi) long. On the Moon, however, lava tubes are much larger, due to the fact that the Moon has only a fraction of the Earth’s gravity (0.1654 g to be exact).
For a lava tube to be detecting using gravity data, it would need to be several kilometers in length and at least one kilometer in height and width. Since the tube in Marius Hills was detectable, it is likely big enough to house a major city. In fact, during a presentation at the 47th Lunar and Planetary Conference, researchers from Purdue University showed GRAIL data that indicated how the tube beneath the MHH could be large enough to house Philadelphia.
Similar evidence of lava tubes has also been discovered on Mars, and possible even Mercury. On Mars in particular, chains of pit craters, broad lava fans, skylights and partially collapsed lava tubes all indicate the presence of stable tubes. Based on this latest study, future mission to the Red Planet (which could include the creation of a habitat) might also entail the investigation of these features.
In fact, lava tubes could become the means through which a human presence is established throughout the Solar System someday!
Venus’ atmosphere is as mysterious as it is dense and scorching. For generations, scientists have sought to study it using ground-based telescopes, orbital missions, and the occasional atmospheric probe. And in 2006, the ESA’s Venus Express mission became the first probe to conduct long-term observations of the planet’s atmosphere, which revealed much about its dynamics.
Using this data, a team of international scientists – led by researchers from the Japan Aerospace and Exploration Agency (JAXA) – recently conducted a study that characterized the wind and upper cloud patterns on the night side of Venus. In addition to being the first of its kind, this study also revealed that the atmosphere behaves differently on the night side, which was unexpected.
The study, titled “Stationary Waves and Slowly Moving Features in the Night Upper Clouds of Venus“, recently appeared in the scientific journal Nature Astronomy. Led by Javier Peralta, the International Top Young Fellow of JAXA, the team consulted data obtained by Venus Express’ suite of scientific instruments in order to study the planet’s previously-unseen cloud types, morphologies, and dynamics.
Whereas plenty of studies have been conducted of Venus’ atmosphere from soace, this was the first time that a study was not focused on the dayside of the planet. As Dr. Peralta explained in an ESA press statement:
“This is the first time we’ve been able to characterize how the atmosphere circulates on the night side of Venus on a global scale. While the atmospheric circulation on the planet’s dayside has been extensively explored, there was still much to discover about the night side. We found that the cloud patterns there are different to those on the dayside, and influenced by Venus’ topography.“
Since the 1960s, astronomers have been aware that Venus’ atmosphere behaves much differently that those of other terrestrial planets. Whereas Earth and Mars have atmospheres that co-rotate at approximately the same speed as the planet, Venus’ atmosphere can reach speeds of more than 360 km/h (224 mph). So while the planet takes 243 days to rotate once on its axis, the atmosphere takes only 4 days.
This phenomena, known as “super-rotation”, essentially means that the atmosphere moves over 60 times faster than the planet itself. In addition, measurements in the past have shown that the fastest clouds are located at the upper cloud level, 65 to 72 km (40 to 45 mi) above the surface. Despite decades of study, atmospheric models have been unable to reproduce super-rotation, which indicated that some of the mechanics were unknown.
“We focused on the night side because it had been poorly explored; we can see the upper clouds on the planet’s night side via their thermal emission, but it’s been difficult to observe them properly because the contrast in our infrared images was too low to pick up enough detail.”
This consisted of observing Venus’ night side clouds with the probe’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS). The instrument gathered hundreds of images simultaneously and different wavelengths, which the team then combined to improve the visibility of the clouds. This allowed the team to see them properly for the first time, and also revealed some unexpected things about Venus’ night side atmosphere.
What they saw was that atmospheric rotation appeared to be more chaotic on the night side than what has been observed in the past on the dayside. The upper clouds also formed different shapes and morphologies – i.e. large, wavy, patchy, irregular and filament-like patterns – and were dominated by stationary waves, where two waves moving in opposite directions cancel each other out and create a static weather pattern.
The 3D properties of these stationary waves were also obtained by combining VIRTIS data with radio-science data from the Venus Radio Science experiment (VeRa). Naturally, the team was surprised to find these kinds of atmospheric behaviors since they were inconsistent with what has been routinely observed on the dayside. Moreover, they contradict the best models for explaining the dynamics of Venus’ atmosphere.
Known as Global Circulation Models (GCMs), these models predict that on Venus, super-rotation would occur in much the same way on both the dayside and the night side. What’s more, they noticed that stationary waves on the night side appeared to coincide with high-elevation features. As Agustin Sánchez-Lavega, a researcher from the University del País Vasco and a co-author on the paper, explained:
“Stationary waves are probably what we’d call gravity waves–in other words, rising waves generated lower in Venus’ atmosphere that appear not to move with the planet’s rotation. These waves are concentrated over steep, mountainous areas of Venus; this suggests that the planet’s topography is affecting what happens way up above in the clouds.“
This is not the first time that scientists have spotted a possible link between Venus’ topography and its atmospheric motion. Last year, a team of European astronomers produced a study that showed how weather patterns and rising waves on the dayside appeared to be directly connected to topographical features. These findings were based on UV images taken by the Venus Monitoring Camera (VMC) on board the Venus Express.
Finding something similar happening on the night side was something of a surprise, until they realized they weren’t the only ones to spot them. As Peralta indicated:
“It was an exciting moment when we realized that some of the cloud features in the VIRTIS images didn’t move along with the atmosphere. We had a long debate about whether the results were real–until we realised that another team, led by co-author Dr. Kouyama, had also independently discovered stationary clouds on the night side using NASA’s Infrared Telescope Facility (IRTF) in Hawaii! Our findings were confirmed when JAXA’s Akatsuki spacecraft was inserted into orbit around Venus and immediately spotted the biggest stationary wave ever observed in the Solar System on Venus’ dayside.“
These findings also challenge existing models of stationary waves, which are expected to form from the interaction of surface wind and high-elevation surface features. However, previous measurements conducted by the Soviet-era Venera landers have indicated that surface winds might too weak for this to happen on Venus. In addition, the southern hemisphere, which the team observed for their study, is quite low in elevation.
And as Ricardo Hueso of the University of the Basque Country (and a co-author on the paper) indicated, they did not detect corresponding stationary waves in the lower cloud levels. “We expected to find these waves in the lower levels because we see them in the upper levels, and we thought that they rose up through the cloud from the surface,” he said. “It’s an unexpected result for sure, and we’ll all need to revisit our models of Venus to explore its meaning.”
From this information, it seems that topography and elevation are linked when it comes to Venus’ atmospheric behavior, but not consistently. So the standing waves observed on Venus’ night side may be the result of some other undetected mechanism at work. Alas, it seems that Venus’ atmosphere – in particular, the key aspect of super-rotation – still has some mysteries for us.
The study also demonstrated the effectiveness of combining data from multiple sources to get a more detailed picture of a planet’s dynamics. With further improvements in instrumentation and data-sharing (and perhaps another mission or two to the surface) we can expect to get a clearer picture of what is powering Venus’ atmospheric dynamics before long.
With a little luck, there may yet come a day when we can model the atmosphere of Venus and predict its weather patterns as accurately as we do those of Earth.
In the coming decades, the world’s largest space agencies hope to mount some exciting missions to the Moon and to Mars. Between NASA, Roscosmos, the European Space Agency (ESA), the Chinese National Space Agency (CNSA) and the Indian Space Research Organization (ISRO), there is simply no shortage of proposals for Lunar bases, crewed missions to Mars, and robotic explorers to both.
However, the Japanese Aerospace Exploration Agency (JAXA) has a different mission in mind when it comes to the coming decades. Instead of exploring the Moon or Mars, they propose exploring the moons of Mars! Known as the Martian Moons Exploration (MMX) mission, the plan is to have a robotic spacecraft fly to Phobos and Deimos to explore their surfaces and return samples to Earth for analysis.
The spacecraft would be deployed sometime in the 2020s, and would be tasked with two main objectives. The first would be to help scientists determine the origins of Phobos and Deimos, which has been a subject of debate for some time. Whereas some believe that these moons are capture asteroids, others have argued that they were created when fragments ejected from Mars (due to giant impacts on the surface) came together.
“MMX will land on Phobos and acquire samples of at least 10 grams from more than 2cm below the surface. Analysis of samples returned to Earth will clarify the nature of the asteroid that led to the formation of the moon. Deimos observations will be limited to flyby imaging, but combined with ground data to be obtained for Phobos, we should be able to constrain its origin in a substantial manner.”
The second objective focuses on the characterization of conditions both on and around the moons of Mars. This includes surface processes on Phobos and Deimos, the nature of the environment in which they orbit, and the global and temporal dynamics of Mars atmosphere – i.e. dust, clouds and water vapor.
“Airless bodies such as asteroids are exposed to space weathering processes,” said Dr. Fujimoto. “In the case of Phobos, an impact event on the surface releases many dust particles. Unlike an asteroid in the interplanetary space, dust particles will not be simply lost but will orbit around Mars and return and hit the Phobos surface. This is regarded as the reason that Phobos has a very thick regolith layer. Knowing this process is to know the attributes of returned samples better.”
Another major objective of this mission is to learn more about small bodies coming from the outer Solar System. As the outermost rocky planet, Mars’ orbit marks the boundary between the terrestrial planets – which have solid surfaces and variable atmospheres (ranging from super-thing to dense) – and the gas and ice giants of the outer Solar System that have highly dense atmospheres.
Because of this, studying Mars’ moons, determining their origin, and learning more about the Martian orbital environment could teach us a lot about the evolution of the Solar System. Not only does such a mission present opportunities to study how planets like Mars formed, but also the process of by which primordial materials were transported between the inner and outer Solar Systems during its early history. As Dr. Fujimoto explained:
“These small bodies were the delivery capsules for water from outside the Frost Line to the Habitable Zone of the solar system, where our planet is situated. Earth was born dry and needed delivery of water for its habitability to be switched on at all. It is likely that one of the (failed) deliveries led to the formation of Phobos, and, sample analysis will tell us about the failed capsule.
“This is obviously the case when the capture idea turns out to be correct. Even for the case of giant impact, the scale of the impact is considered to be not too gigantic to alter fully the materials, implying that sample analysis would tell us something about the impactor asteroid.”
As it stands, the probe is scheduled to launch in September 2024, taking advantage of the fact that Earth and Mars will be at the nearest point to each other in their orbits at this time. It will arrive around Mars by 2025, conduct its studies for a three-year period, and then return to Earth by July of 2029. Once there, it will rely on a suite of scientific instruments to conduct surveys and obtain samples.
These instruments include a Neutron and Gamma-ray Spectrometer (NGRS), a Near-Infrared Spectrometer (NIRS), a Wide Angle Multiband Camera (WAM), a Telescopic Camera (TL), a Circum-Martian Dust Monitor (CMDM), a Mass Spectrum Analyzer (MSA), and a Light Detection and Ranging (LIDAR) instrument.
The mission will also leverage some key partnerships that JAXA is currently engaged in. These include an agreement reached with NASA back in late March to include the Neutron and Gamma-ray Spectrometer (NGRS) in the MMX’s instrument suite. And in April, JAXA and the National Center for Space Studies (CNES) signed an Implementation Agreement (IA) that would allow the French national space agency to participate in the mission as well.
If all goes as planned, JAXA will be spending the next decade gathering information that could bridge findings made by Lunar and Martian missions. Whereas lunar research will reveal things about the history of the Moon, and Martian missions will offer new insights into Mars’ geology and evolution (and perhaps if life still exists there!), the MMX mission will reveal things about the history of Mars’ moons and the early Solar System as a whole.
Other proposals that JAXA is currently working on include the Jupiter Icy Moons Explorer (JUICE) and SPICA, two missions that will explore Jupiter’s Galilean Moons and conduct infrared astronomy (respectively) in the coming decade.