A year and a half before NASA’s Double-Asteroid Deflection Test (DART) changed the course of a space rock, astronomers peered at a fear-inducing object near Earth.
Thankfully, when Apophis distantly flew past Earth in March 2021, new measurements revealed that it won’t pose a problem for at least a century. And when the time comes, a mission like DART could mitigate the threat.
But to determine how the September 26 strike of the small asteroid Dimorphos might also have changed the trip around the Sun that its larger partner, Didymos, takes, a mission called ACROSS will need to know Didymos’ precise location.
Recently, astronomers accomplished an important first step towards this goal: they finally caught Didymos blocking distant starlight.
ACROSS, or Asteroid Collaborative Research via Occultation Systematic Survey, successfully pin-pointed Didymos passing in front of background starlight for just 0.13 seconds on Saturday (October 15), the European Space Agency (ESA) reports. But it wasn’t easy — ESA officials say that the efforts of the ACROSS collective were “enormous and unsuccessful for several weeks.”
ACROSS leaned on the incredible work of another ESA mission, called Gaia, that is currently surveying one billion stars in the Milky Way. The cutting-edge work of the 8-year-old mission has already manifested in three data releases, the most recent in June of this year. Astronomers were able to track Didymos in Gaia data, helping them track its position over time.
Stellar occultation — that is, when an object passes in front of a distant star from our point of view — is a helpful phenomenon that, in the past, has aided the search for objects past the orbit of Neptune. Closer to home, it’s helped reveal asteroids that travel around the Sun between the orbits of Mars and Jupiter. But near-Earth asteroids, or NEAs, are much harder to find.
“NEAs move fast and are small,” Paolo Tanga, project leader of ACROSS and planetary scientist of the Côte d’Azur Observatory in France, says in the ESA statement. “Thus producing shorter events and much narrower shadows projected on the ground.”
But like Apophis, some NEAs could be menacing. Now that Didymos has been spotted through stellar occultation, however, astronomers can evaluate the progress of possibly-life-saving kinetic deflection tests like DART.
In October 2024, ESA will also launch a mission to check out the aftermath of DART’s impact up-close. This spacecraft, called HERA, is currently expected to reach Didymos and Dimorphos in December 2026.
Giant mantle plume suggests Mars is more active than previously believed
Although most volcanic and tectonic activity on Mars occurred during the first 1.5 billion years of its geologic history, recent volcanism, tectonism, and active seismicity in Elysium Planitia reveal ongoing activity. However, this recent pulse in volcanism and tectonics is unexpected on a cooling Mars.
A new study by scientists from the University of Arizona presents multiple lines of evidence that reveal the presence of a giant active mantle plume on present-day Mars. The study challenges current views of Martian geodynamic evolution with a report on discovering an active mantle plume pushing the surface upward and causing earthquakes and volcanic eruptions.
Jeff Andrews-Hanna, an associate professor of planetary science at the LPL, said, “We have strong evidence for mantle plumes being active on Earth and Venus, but this isn’t expected on a small and supposedly cold world like Mars. Mars was most active 3 to 4 billion years ago, and the prevailing view is that the planet is essentially dead today.”
Adrien Broquet, a postdoctoral research associate at the UArizona Lunar and Planetary Laboratory, said, “A tremendous amount of volcanic activity early in the planet’s history built the tallest volcanoes in the solar system and blanketed most of the northern hemisphere in volcanic deposits. What little activity has occurred in recent history is typically attributed to passive processes on a cooling planet.”
The Elysium Planitia plain, located in the northern lowlands of Mars near the equator, caught the attention of scientists due to a startling level of activity. Elysium Planitia has undergone significant eruptions over the past 200 million years, in contrast to other volcanic zones on Mars that haven’t experienced significant activity in billions of years.
Andrews-Hanna said, “Previous work by our group found evidence in Elysium Planitia for the youngest volcanic eruption known on Mars. It created a small explosion of volcanic ash around 53,000 years ago, which in geologic time is essentially yesterday.”
The Cerberus Fossae, a series of young fissures that span more than 800 miles over the Martian surface, is the source of the volcanism in Elysium Planitia. Recently, the InSight team at NASA discovered that almost all marsquakes originate from this area. Although the young age of this volcanic and tectonic activity had been established, its root cause was still unknown.
Broquet said, “We know that Mars does not have plate tectonics, so we investigated whether the activity we see in the Cerberus Fossae region could be the result of a mantle plume.”
The scientists discovered evidence of a similar series of events on Mars when they examined the features of Elysium Planitia. One of the highest places in Mars’ vast northern lowlands, the surface has been raised by more than a mile. The existence of a mantle plume is compatible with the uplift being supported from deep within the globe, according to analyses of minor fluctuations in the gravitational field.
Additional measurements supported the theory that something pushed the surface up after the craters formed by revealing that the floor of impact craters is inclined in the direction of the plume. Finally, when scientists used a tectonic model to the region, they discovered that the only explanation for the extension that created the Cerberus Fossae was the existence of a massive plume 2,500 miles wide.
Broquet said, “In terms of what you expect to see with an active mantle plume, Elysium Planitia is checking all the right boxes. The finding poses a challenge for models used by planetary scientists to study the thermal evolution of planets. This mantle plume has affected an area of Mars roughly equivalent to that of the continental United States. Future studies will have to find a way to account for a huge mantle plume that wasn’t expected to be there.”
“We used to think InSight landed in one of the most geologically boring regions on Mars – a nice flat surface that should roughly represent the planet’s lowlands. Instead, our study demonstrates that InSight landed right on top of an active plume head.”
“Having an active mantle plume on Mars today is a paradigm shift for our understanding of the planet’s geologic evolution, similar to when analyses of seismic measurements recorded during the Apollo era demonstrated the moon’s core to be molten.”
Scientists noted, “Their findings could also have implications for life on Mars. The studied region experienced floods of liquid water in its recent geologic past, though the cause has remained a mystery. The same heat from the plume fueling ongoing volcanic and seismic activity could also melt ice to make the floods – and drive chemical reactions that could sustain life deep underground.”
Andrews-Hanna said, “Microbes on Earth flourish in environments like this, and that could be true on Mars, as well. The discovery goes beyond explaining the enigmatic seismic activity and resurgence in volcanic activity. Knowing that there is an active giant mantle plume underneath the Martian surface raises important questions regarding how the planet has evolved. We’re convinced that the future has more surprises in store.”
- Broquet, A., Andrews-Hanna, J.C. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nat Astron (2022). DOI: 10.1038/s41550-022-01836-3
NASA capsule flies over Apollo landing sites, heads home
CAPE CANAVERAL, Fla. –
NASA’s Orion capsule and its test dummies swooped one last time around the moon Monday, flying over a couple Apollo landing sites before heading home.
Orion will aim for a Pacific splashdown Sunday off San Diego, setting the stage for astronauts on the next flight in a couple years.
The capsule passed within 80 miles (130 kilometres) of the far side of the moon, using the lunar gravity as a slingshot for the 237,000-mile (380,000-kilometre) ride back to Earth. It spent a week in a wide, sweeping lunar orbit.
Once emerging from behind the moon and regaining communication with flight controllers in Houston, Orion beamed back photos of a close-up moon and a crescent Earth — Earthrise — in the distance.
“Orion now has its sights set on home,” said Mission Control commentator Sandra Jones.
The capsule also passed over the landing sites of Apollo 12 and 14. But at 1,200 miles (1,900 kilometres) up, it was too high to make out the descent stages of the lunar landers or anything else left behind by astronauts more than a half-century ago. During a similar flyover two weeks ago, it was too dark for pictures. This time, it was daylight.
Deputy chief flight director Zebulon Scoville said nearby craters and other geologic features would be visible in any pictures, but little else.
“It will be more of a tip of the hat and a historical nod to the past,” Scoville told reporters last week.
The three-week test flight has exceeded expectations so far, according to officials. But the biggest challenge still lies ahead: hitting the atmosphere at more than 30 times the speed of sound and surviving the fiery reentry.
Orion blasted off Nov. 16 on the debut flight of NASA’s most powerful rocket ever, the Space Launch System or SLS.
The next flight — as early as 2024 — will attempt to carry four astronauts around the moon. The third mission, targeted for 2025, will feature the first lunar landing by astronauts since the Apollo moon program ended 50 years ago this month.
Apollo 17 rocketed away Dec. 7, 1972, from NASA’s Kennedy Space Center, carrying Eugene Cernan, Harrison Schmitt and Ron Evans. Cernan and Schmitt spent three days on the lunar surface, the longest stay of the Apollo era, while Evans orbited the moon. Only Schmitt is still alive.
Using atomic clocks in space to solve dark matter mystery
A team of international scientists is proposing to send atomic clocks into space to detect and understand enigmatic dark matter.
Dark matter is a mystery that has plagued researchers for decades. This unknown essence represents 85% of all matter in the Universe, and although its effects can be observed, it has not been directly detected. Experts from the University of Delaware, the University of California, and the University of Tokyo are collaborating to solve this longstanding mystery by sending atomic clocks into space.
The research, ‘Direct detection of ultralight dark matter bound to the Sun with space quantum sensors,’ which is published in Nature Astronomy, plans to send two atomic clocks into the inner reaches of the solar system to search for ultralight dark matter that has wavelike properties that may affect the operation of the clocks.
What are atomic clocks?
Atomic clocks tell time by measuring the rapid oscillations of atoms and are already utilised in space to enable the Global Positioning System (GPS). In the future, space clocks could help navigate spacecraft and provide links to Earth-based cocks.
All clocks mark time by using some form of a repetitive process, such as a swinging pendulum. However, atomic clocks use laser technology to manipulate and measure the oscillations of atoms which are extremely fast. For example, a clock based on strontium atoms ticks 430 trillion times per second, and atomic clocks are exceedingly more precise than any mechanical devices.
Historically, atomic clocks can cover the size of a couple of tables, but recent advances in precision and portability mean that some atomic clocks can now fit into a van, with NASA’s Deep Space Atomic Clock being even smaller, at around the size of a toaster.
Nevertheless, different types of clocks, based on much higher frequencies, have been developed over the last 15 years, such as optical clocks that are orders of magnitude more precise and will not lose even a second of time over billions of years.
Marianna Safronova, a physicist at the University of Delaware, said: “We now have portable clocks, and it’s fun to think about how you would go about sending such high-precision clocks to space and establish what great things we can do.
“It is a beautiful synergy between a quantum expert and particle theorists, and we are working on new ideas at the intersection of these two fields.”
Unravelling the mysterious properties of dark matter
The proposed research would send space clocks closer to the Sun than Mercury – an area they believe there is more dark matter to detect. These include atomic, nuclear, and molecular clocks that are currently being developed and are otherwise known as quantum sensors.
Safronova explained: “This was inspired by the Parker Solar Probe, the ongoing NASA mission that sent a spacecraft closer to the Sun than any other spacecraft has gone before. It has nothing to do with quantum sensors or clocks, but it showed that you could send a satellite very close to the Sun, sensing new conditions and making discoveries. That is much closer to the Sun than what we are proposing here.”
The aim of the study is to investigate ultralight dark matter, which the researchers believe could make a huge halo-like region that is bound to the Sun. Ultralight dark matter could cause the energies of atoms to oscillate, which will change how the clock ticks, although this effect depends on the atoms the clock uses. The researchers then monitor the differences in the clocks to look for dark matter.
“It has very specific properties and is a very specific dark matter that is detectable by clocks. What is observable is the ratio of those two clock frequencies. That ratio should oscillate if such dark matter exists,” Safronova said.
She explained that nuclear clocks, which are based on nuclear energy levels rather than atomic energy levels, may be the best clock for this research. She is currently involved in a project to build a prototype funded by the European Research Council.
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