Matt Williams is a space journalist and science communicator for Universe Today and Interesting Engineering. He's also a science fiction author, podcaster (Stories from Space), and Taekwon-Do instructor who lives on Vancouver Island with his wife and family.
Visualization from the Goddard Earth the Observing System Forward Processing (GEOS FP), which shows the presence of aerosols in Earth's atmosphere. Credit: NASA/Joshua Stevens/Adam Voiland
Stand outside and take deep breath. Do you know what you’re breathing? For most people, the answer is simple – air. And air, which is essential to life as we know it, is composed of roughly twenty-percent oxygen gas (O²) and seventy-eight percent nitrogen gas (N²). However, within the remaining one-percent and change are several other trace gases, as well as few other ingredients that are not always healthy.
Star density map, created from the second data release of ESA’s Gaia mission. Credit: Galaxy Map / K. Jardine
In December of 2013, the European Space Agency (ESA) launched the Gaia mission, a space observatory designed to measure the positions of movements of celestial bodies. Over the course of its five-year mission, this observatory has been studying a total of 1 billion objects – including distant stars, planets, comets, asteroids, quasars, etc. – for the sake of creating the largest and most precise 3D space catalog ever made.
Artist's impression of the spiral structure of the Milky Way with two major stellar arms and a bar. Credit: NASA/JPL-Caltech/ESO/R. Hurt
Since the birth of modern astronomy, scientists have sought to determine the full extent of the Milky Way galaxy and learn more about its structure, formation and evolution. According to current theories, it is widely believed that the Milky Way formed shortly after the Big Bang (roughly 13.51 billion years ago). This was the result of the first stars and star clusters coming together, as well as the accretion of gas directly from the Galactic halo.
Artist's concept of Earth-like exoplanets, which (according to new research) need to strike the careful balance between water and landmass. Credit: NASA
Ever since the first exoplanet was confirmed in 1992, astronomers have found thousands of worlds beyond our Solar System. With more and more discoveries happening all the time, the focus of exoplanet research has begun to slowly shift from exoplanet discovery to exoplanet characterization. Essentially, scientists are now looking to determine the composition of exoplanets to determine whether or not they could support life.
A key part of this process is figuring out how much water exists on exoplanets, which is essential to life as we know it. During a recent scientific conference, a team of scientists presented new research that indicates that water is likely to be a major component of those exoplanets which are between two to four times the size of Earth. These findings will have serious implications when it comes to the search for life beyond our Solar System.
Image showing the distribution of surface ice at the Moon's south pole (left) and north pole (right), detected by NASA's Moon Mineralogy Mapper instrument. Credits: NASA
When it comes right down to it, the Moon is a pretty hostile environment. It’s extremely cold, covered in electrostatically-charged dust that clings to everything (and could cause respiratory problems if inhaled), and its surface is constantly bombarded by radiation and the occasional meteor. And yet, the Moon also has a lot going for it as far as establishing a human presence there is concerned.
This 1.5 tonne building block was produced as a demonstration of 3D printing techniques using lunar soil. The design is based on a hollow closed-cell structure – reminiscent of bird bones – to give a good combination of strength and weight. Credit: ESA
In the coming decades, many space agencies hope to conduct crewed missions to the Moon and even establish outposts there. In fact, between NASA, the European Space Agency (ESA), Roscosmos, and the Indian and Chinese space agencies, there are no shortages of plans to construct lunar bases and settlements. These will not only establish a human presence on the Moon, but facilitate missions to Mars and deeper into space.
For instance, the ESA is planning on building an “international lunar village” on the Moon by the 2030s. As the spiritual successor to the International Space Station (ISS), this village would also allow for scientific research in a lunar environment. Currently, European researchers are planning how to go about constructing this village, which includes conducting experiments with lunar dust simulants to create bricks.
To put it simply, the entire surface of the Moon is covered in dust (aka. regolith) that is composed of fine particles of rough silicate. This dust was formed over the course of billions of years by constant meteorite impacts which pounded the silicate mantle into fine particles. It has remained in a rough and fine state due to the fact that the lunar surface experiences no weathering or erosion (due to the lack of an atmosphere and liquid water).
Artist’s concept for a multi-dome lunar base, which would be constructed by 3D-printing robots using lunar dust (regolith). Credits: ESA/Foster + Partners
Because it is so plentiful, reaching depths of 4-5 meters (13-16.5 feet) in some places – and up to 15 meters (49 feet) in the older highland areas – regolith is considered by many space agencies to be the building material of choice for lunar settlements. As Aidan Cowley, the ESA’s science advisor and an expert when it comes to lunar soil, explained in a recent ESA press release:
“Moon bricks will be made of dust. You can create solid blocks out of it to build roads and launch pads, or habitats that protect your astronauts from the harsh lunar environment.”
In addition to taking advantage of a seemingly inexhaustible local resource, the ESA’s plans to use lunar regolith to create this base and related infrastructure demonstrates their commitment to in-situ resource utilization. Basically, bases on the Moon, Mars, and other locations in the Solar System will need to be as self-sufficient as possible to reduce reliance on Earth for regular shipments of supplies – which would both expensive and resource-exhaustive.
To test how lunar regolith would fare as a building material, ESA scientists have been using Moon dust simulants harvested right here on Earth. As Aiden explained, regolith on both Earth and the Moon are the product of volcanism and are basically basaltic material made up of silicates. “The Moon and Earth share a common geological history,” he said, “and it is not difficult to find material similar to that found on the Moon in the remnants of lava flows.”
ESA’s 3D-printed lunar base concept, based on the design produced by the architectural design and engineering firm Foster+Partners. Credit: ESA/Foster + Partners
The simulant were harvested from the region around Cologne, Germany, that were volcanically active about 45 million years ago. Using volcanic powder from these ancient lava flows, which was determined to be a good match for lunar dust, researchers from the European Astronaut Center (EAC) began using the powder (which they’ve named EAC-1) to fashioning prototypes of the bricks that would be used to created the lunar village.
Spaceship EAC, an ESA initiative designed to tackle the challenges of crewed spaceflight, is also working with EAC-1 to develop the technologies and concepts that will be needed to create a lunar outpost and for future missions to the Moon. One of their projects centers on how to use the oxygen in lunar dust (which accounts for 40% of it) to help astronauts have extended stays on the Moon.
But before the ESA can sign off on lunar dust as a building material, a number of tests still need to be conducted. These include recreating the behavior of lunar dust in a radiation environment to simulate their electrostatic behavior. For decades, scientists have known that lunar dust is electrically-charged because of the way it is constantly bombarded by solar and cosmic radiation.
This is what causes it to lift off the surface and cling to anything it touches (which the Apollo 11 astronauts noticed upon returning to the Lunar Module). As Erin Transfield – a member of ESA’s lunar dust topical team – indicated, scientists still do not fully understand lunar dust’s electrostatic nature, which could pose a problem when it comes to using it as a building material.
What’s more, the radiation-environment experiments have not produced any conclusive results yet. As a biologist who dreams of being the first woman on the Moon, Transfield indicated that more research is necessary using actual lunar dust. “This gives us one more reason to go back to the Moon,” she said. “We need pristine samples from the surface exposed to the radiation environment.”
Beyond establishing a human presence on the Moon and allowing for deep-space missions, the construction of the ESA’s proposed lunar village would also offer opportunities to leverage new technologies and forge partnerships between the public and private sector. For instance, the ESA has collaborated with the architectural design firm Foster + Partners to come up with the design for their lunar village, and other private companies have been recruited to help investigate other aspects of building it.
This mission, a joint effort between the ESA and Roscosmos, will involve a Russian-built lander setting down in the Moon’s South Pole-Aitken Basin, where the PROSPECT probe will deploy and drill into the surface to retrieve samples of ice. Going forward, the ESA’s long-term plans also call for a series of missions to the Moon beginning in the 2020s that would involve robot workers paving the way for human explorers to land later.
In the coming decades, the intentions of the world’s leading space agencies are clear – not only are we going back to the Moon, but we intend to stay there! To that end, considerable resources are being dedicated towards researching and developing the necessary technologies and concepts needed to make this happen. By the 2030s, we might just see astronauts (and even private citizens) coming and going from the Moon with regular frequency.
And be sure to check out this video about the EAC’s efforts to study lunar regolith, courtesy of the ESA:
Alberta Aurora Chasers capture STEVE, the new-to-science upper atmospheric phenomenon, on the evening of April 10th, 2018 in Prince George, British Columbia, Canada. Credit: Ryan Sault
Since time immemorial, people living in the Arctic Circle or the southern tip of Chile have looked up at the night sky and been dazzled by the sight of the auroras. Known as the Aurora Borealis in the north and Aurora Australis in the south (the “Northern Lights” and “Southern Lights”, respectively) these dazzling displays are the result of interactions in the ionosphere between charged solar particles and the Earth’s magnetic field.
However, in recent decades, amateur photographers began capturing photos of what appeared to be a new type of aurora – known as STEVE. In 2016, it was brought to the attention of scientists, who began trying to explain what accounted for the strange ribbons of purple and white light in the night sky. According to a new study, STEVE is not an aurora at all, but an entirely new celestial phenomenon.
The study recently appeared in the Geophysical Research Letters under the title “On the Origin of STEVE: Particle Precipitation or Ionospheric Skyglow?“. The study was conducted by a team of researchers from the Department of Physics and Astronomy from the University of Calgary, which was led by Beatriz Gallardo-Lacourt (a postdoctoral associate), and included Yukitoshi Nishimura – an assistant researcher of the Department of Atmospheric and Oceanic Sciences at the University of California.
STEVE, as imaged by Dave Markel in the skies above northern Canada. Copyright: davemarkelphoto
STEVE first became known to scientists thanks to the efforts of the Alberta Aurora Chasers (AAC), who occasionally noticed these bright, thin streams of white and purple light running from east to west in the night sky when photographing the aurora. Unlike auroras, which are visible whenever viewing conditions are right, STEVE was only visible a few times a year and could only be seen at high latitudes.
Initially, the photographers thought the light ribbons were the result of excited protons, but these fall outside the range of wavelengths that normal cameras can see and require special equipment to image. The AAC eventually named the light ribbons “Steve” – a reference to the 2006 film Over the Hedge. By 2016, Steve was brought to the attention of scientists, who turned the name into a backronym for Strong Thermal Emission Velocity Enhancement.
For their study, the research team analyzed a STEVE event that took place on March 28th, 2008, to see if it was produced in a similar fashion to an aurora. To this end, they considered previous research that was conducted using satellites and ground-based observatories, which included the first study on STEVE (published in March of 2018) conducted by a team of NASA-led scientists (of which Gallardo-Lacourt was a co-author).
This study indicated the presence of a stream of fast-moving ions and super-hot electrons passing through the ionosphere where STEVE was observed. While the research team suspected the two were connected, they could not conclusively state that the ions and electrons were responsible for producing it. Building on this, Gallardo-Lacourt and her colleagues analyzed the STEVE event that took place in March of 2008.
Rays of aurora borealis reach 60 miles and higher over the Pacific Northwest on Jan. 20, 2016 in this photo taken by astronauts Scott Kelly and Tim Peake from the International Space Station. Credit: NASA
They began by using images from ground-based cameras that record auroras over North America, which they then combined with data from the National Oceanic and Atmospheric Administration‘s (NOAA) Polar Orbiting Environmental Satellite 17 (POES-17). This satellite, which can measure the precipitation of charged particles into the ionosphere, was passing directly over the ground-based cameras during the STEVE event.
What they found was that the POES-17 satellite detected no charged particles raining down on the ionosphere during the event. This means that STEVE is not likely to be caused by the same mechanism as an aurora, and is therefore an entirely new type of optical phenomenon – which the team refer to as “skyglow”. As Gallardo-Lacourt explained in an AGU press release:
“Our main conclusion is that STEVE is not an aurora. So right now, we know very little about it. And that’s the cool thing, because this has been known by photographers for decades. But for the scientists, it’s completely unknown.”
Looking ahead, Galladro-Lacourt and her colleagues seek to test the conclusions of the NASA-led study. In short, they want to find out whether the streams of fast ions and hot electrons that were detected in the ionosphere are responsible for STEVE, or if the light is being produced higher up in the atmosphere. One thing is for certain though; for aurora chasers, evening sky-watching has become more interesting!
Artist's impression of a Near-Earth Asteroid passing by Earth. Credit: ESA
Roughly 4.5 billion years ago, scientists theorize that Earth experienced a massive impact with a Mars-sized object (named Theia). In accordance with the Giant Impact Hypothesis, this collision placed a considerable amount of debris in orbit, which eventually coalesced to form the Moon. And while the Moon has remained Earth’s only natural satellite since then, astronomers believe that Earth occasionally shares its orbit with “mini-moons”.
These are essentially small and fast-moving asteroids that largely avoid detection, with only one having been observed to date. But according to a new study by an international team of scientists, the development of instruments like the Large Synoptic Survey Telescope (LSST) could allow for their detection and study. This, in turn, will present astronomers and asteroid miners with considerable opportunities.
The study which details their findings recently appeared in the Frontiers in Astronomy and Space Sciences under the title “Earth’s Minimoons: Opportunities for Science and Technology“. The study was led by Robert Jedicke, a researcher from the University of Hawaii at Manoa, and included members from the Southwest Research Institute (SwRI), the University of Washington, the Luleå University of Technology, the University of Helsinki, and the Universidad Rey Juan Carlos.
As a specialist in Solar System bodies, Jedicke has spent his career studying the orbit and size distributions of asteroid populations – including Main Belt and Near Earth Objects (NEOs), Centaurs, Trans-Neptunian Objects (TNOs), comets, and interstellar objects. For the sake of their study, Jedicke and his colleagues focused on objects known as temporarily-captured orbiters (TCO) – aka. mini-moons.
These are essentially small rocky bodies – thought to measure up to 1-2 meters (3.3 to 6.6 feet) in diameter – that are temporarily gravitationally bound to the Earth-Moon system. This population of objects also includes temporarily-captured flybys (TCFs), asteroids that fly by Earth and make at least one revolution of the planet before escaping orbit or entering our atmosphere.
As Dr. Jedicke explained in a recent Science Dailynews release, these characteristics is what makes mini-moons particularly hard to observe:
“Mini-moons are small, moving across the sky much faster than most asteroid surveys can detect. Only one minimoon has ever been discovered orbiting Earth, the relatively large object designated 2006 RH120, of a few meters in diameter.”
This object, which measured a few meters in diameter, was discovered in 2006 by the Catalina Sky Survey (CSS), a NASA-funded project supported by the Near Earth Object Observation Program (NEOO) that is dedicated to discovering and tracking Near-Earth Asteroids (NEAs). Despite improvements over the past decade in ground-based telescopes and detectors, no other TCOs have been detected since.
Artist rendering of the LSST observatory (foreground) atop Cerro Pachón in Chile. Credit: Large Synoptic Survey Telescope Project Office.
After reviewing the last ten years of mini-moon research, Jedicke and colleagues concluded that existing technology is only capable of detecting these small, fast moving objects by chance. This is likely to change, according to Jedicke and his colleagues, thanks to the advent of the Large Synoptic Survey Telescope (LSST), a wide-field telescope that is currently under construction in Chile.
Once complete, the LSST will spend the ten years investigating the mysteries of dark matter and dark energy, detecting transient events (e.g. novae, supernovae, gamma ray bursts, gravitational lensings, etc.), mapping the structure of the Milky Way, and mapping small objects in the Solar System. Using its advanced optics and data processing techniques, the LSST is expected to increase the number of cataloged NEAs and Kuiper Belt Objects (KBOs) by a factor of 10-100.
But as they indicate in their study, the LSST will also be able to verify the existence of TCOs and track their paths around our planet, which could result in exciting scientific and commercial opportunities. As Dr. Jedicke indicated:
“Mini-moons can provide interesting science and technology testbeds in near-Earth space. These asteroids are delivered towards Earth from the main asteroid belt between Mars and Jupiter via gravitational interactions with the Sun and planets in our solar system. The challenge lies in finding these small objects, despite their close proximity.”
Time-lapse photo of the sky above the LSST construction site in Chile. Credit: LSST
When it is completed in a few years, it is hoped that the LSST will confirm the existence of mini-moons and help track their orbits around Earth. This will be possible thanks to the telescope’s primary mirror (which measures 8.4 meters (27 feet) across) and its 3200 megapixel camera – which has a tremendous field of view. As Jedicke explained, the telescope will be able to cover the entire night sky more than once a week and collect light from faint objects.
With the ability to detect and track these small, fast objects, low-cost missions may be possible to mini-Moons, which would be a boon for researchers seeking to learn more about asteroids in our Solar System. As Dr Mikael Granvik – a researcher from the Luleå University of Technology, the University of Helsinki, and a co-author on the paper – indicated:
“At present we don’t fully understand what asteroids are made of. Missions typically return only tiny amounts of material to Earth. Meteorites provide an indirect way of analyzing asteroids, but Earth’s atmosphere destroys weak materials when they pass through. Mini-moons are perfect targets for bringing back significant chunks of asteroid material, shielded by a spacecraft, which could then be studied in detail back on Earth.”
As Jedicke points out, the ability to conduct low-cost missions to objects that share Earth’s orbit will also be of interest to the burgeoning asteroid mining industry. Beyond that, they also offer the possibility of increasing humanity’s presence in space.
“Once we start finding mini-moons at a greater rate they will be perfect targets for satellite missions,” he said. “We can launch short and therefore cheaper missions, using them as testbeds for larger space missions and providing an opportunity for the fledgling asteroid mining industry to test their technology… I hope that humans will someday venture into the solar system to explore the planets, asteroids and comets — and I see mini-moons as the first stepping stones on that voyage.”
Artist illustration of Habitation Module aboard the Deep Space Gateway. Credit: Lockheed Martin
In their pursuit of returning astronauts to the Moon, and sending crewed missions to Mars, NASA has contracted with a number of aerospace companies to develop all the infrastructure it will need. In addition to the Space Launch System (SLS) and the Orion spacecraft – which will fly the astronauts into space and see them safety to their destinations – they have teamed up with Lockheed Martin and other contractors to develop the Deep Space Gateway.
This orbiting lunar habitat will not only facilitate missions to and from the Moon and Mars, it will also allow human beings to live and work in space like never before. On Thursday, August 16th, Lockheed Martin provided a first glimpse of what one the of habitats aboard the Deep Space Gateway would look like. It all took place at the Kennedy Space Center in Florida, where attendees were given a tour of the habitat prototype.
At it’s core, the habitat uses the Donatello Multi-Purpose Logistics Module (MPLM), a refurbished module designed by the Italian Space Agency that dates back to the Space Shuttle era. Like all MPLMs, the Donatello is a pressurized module that was intended to carry equipment, experiments and supplies to and from the International Space Station aboard the Space Shuttle.
While the Donatello was never sent into space, Lockheed Martin has re-purposed it to create their prototype habitat. Measuring 6.7 meters (22 feet) long and 4.57 meters (15 feet) wide, the pressurized capsule is designed to house astronauts for a period of 30 to 60 days. According to Bill Pratt, the program’s manager, it contains racks for science, life support systems, sleep stations, exercise machines, and robotic workstations.
The team also relied on “mixed-reality prototyping” to create the prototype habitat, a process where virtual and augmented reality are used to solve engineering issues in the early design phase. As Pratt explained in an interview with the Orlando Sentinel, their design makes optimal use of limited space, and also seeks to reuse already-build components:
“You think of it as an RV in deep space. When you’re in an RV, your table becomes your bed and things are always moving around, so you have to be really efficient with the space. That’s a lot of what we are testing here… We want to get to the moon and to Mars as quickly as possible, and we feel like we actually have a lot of stuff that we can use to do that.”
This habitat is one of several components that will eventually go into creating the Deep Space Gateway. These will include the habitat, an airlock, a propulsion module, a docking port and a power bus, which together would weigh 68 metric tonnes (75 US tons). This makes it considerably smaller than the International Space Station (ISS), which weighs in at a hefty 408 metric tonnes (450 US tons).
Artist’s impression of the Deep Space Gateway, currently under development by Lockheed Martin. Credit: NASA
Moreover, the DSG is one of several components that will be used to return astronauts to the Moon and to Mars. As noted, these include the Space Launch System (SLS), which will be the most powerful launch vehicle since the Saturn V (the rocket that carried the Apollo astronauts to the Moon) and the Orion Multi-Purpose Crew Vehicle (MPCV), which will house the crew.
However, for their planned missions to Mars, NASA is also looking to develop the Deep Space Transport and the Mars Base Camp and Lander. The former calls for a reusable vehicle that would rely on a combination of Solar Electric Propulsion (SEP) and chemical propulsion to transport crews to and from the Gateway, whereas the latter would orbit Mars and provide the means to land on and return from the surface.
All told, NASA has awarded a combined $65 million to six contractors – Lockheed Martin, Boeing, Sierra Nevada Corp.’s Space Systems, Orbital ATK, NanoRacks and Bigelow Aerospace – to build the habitat prototype by the end of the year. The agency will then review the proposals to determine which systems and interfaces will be incorporated into the design of the Deep Space Gateway.
In the meantime, development of the Orion spacecraft continues at the Kennedy Space Center, which recently had its heat shields attached. Next month, the European Space Agency (ESA) will also be delivering the European Service Module to the Kennedy Space Center, which will be integrated with the Orion crew module and will provide it with the electricity, propulsion, thermal control, air and water it will need to sustain a crew in space.
Artist’s impression of the Mars Base Camp in orbit around Mars. When missions to Mars begin, one of the greatest risks will be that posed by space radiation. Credit: Lockheed Martin
Once this is complete, NASA will begin the process of integrating the spacecraft with the SLS. NASA hopes to conduct the first uncrewed mission using the Orion spacecraft by 2020, in what is known as Exploration Mission-1 (EM-1). Exploration Mission-2 (EM-2), which will involve a crew performing a lunar flyby test and returning to Earth, is expected to take place by mid-2022.
Development on the the Deep Space Transport and the Mars Base Camp and Lander is also expected to continue. Whereas the Gateway is part of the first phase of NASA’s “Journey to Mars” plan – the “Earth Reliant” phase, which involves exploration near the Moon using current technologies – these components will be part of Phase II, which is on developing long-duration capabilities beyond the Moon.
If all goes according to plan, and depending on the future budget environment, NASA still hopes to mount a crewed mission to Mars by the 2030s.
According to a new study, evidence of life (aka. biosignatures) could be found by examining ejecta from extra-solar planets caused by asteroid impacts. Image: NASA/JPL-Caltech/Univ. of Arizona
In recent years, the number of confirmed extra-solar planets has risen exponentially. As of the penning of the article, a total of 3,777 exoplanets have been confirmed in 2,817 star systems, with an additional 2,737 candidates awaiting confirmation. What’s more, the number of terrestrial (i.e. rocky) planets has increased steadily, increasing the likelihood that astronomers will find evidence of life beyond our Solar System.
Unfortunately, the technology does not yet exist to explore these planets directly. As a result, scientists are forced to look for what are known as “biosignatures”, a chemical or element that is associated with the existence of past or present life. According to a new study by an international team of researchers, one way to look for these signatures would be to examine material ejected from the surface of exoplanets during an impact event.
Artist’s impression of what an asteroid hitting the Earth might look like. Credit: NASA/Don Davis.
As they indicate in their study, most efforts to characterize exoplanet biospheres have focused on the planets’ atmospheres. This consists of looking for evidence of gases that are associated with life here on Earth – e.g. carbon dioxide, nitrogen, etc. – as well as water. As Cataldi told Universe Today via email:
“We know from Earth that life can have a strong impact on the composition of the atmosphere. For example, all the oxygen in our atmosphere is of biological origin. Also, oxygen and methane are strongly out of chemical equilibrium because of the presence of life. Currently, it is not yet possible to study the atmospheric composition of Earth-like exoplanets, however, such a measurement is expected to become possible in the foreseeable future. Thus, atmospheric biosignatures are the most promising way to search for extraterrestrial life.”
However, Cataldi and his colleagues considered the possibility of characterizing a planet’s habitability by looking for signs of impacts and examining the ejecta. One of the benefits of this approach is that ejecta escapes lower gravity bodies, such as rocky planets and moons, with the greatest ease. The atmospheres of these types of bodies are also very difficult to characterize, so this method would allow for characterizations that would not otherwise be possible.
And as Cataldi indicated, it would also be complimentary to the atmospheric approach in a number of ways:
“First, the smaller the exoplanet, the more difficult it is to study its atmosphere. On the contrary, smaller exoplanets produce larger amounts of escaping ejecta because their surface gravity is lower, making ejecta from smaller exoplanet easier to detect. Second, when thinking about biosignatures in impact ejecta, we think primarily of certain minerals. This is because life can influence the mineralogy of a planet either indirectly (e.g. by changing the composition of the atmosphere and thus allowing new minerals to form) or directly (by producing minerals, e.g. skeletons). Impact ejecta would thus allow us to study a different sort of biosignature, complementary to atmospheric signatures.”
Another benefit to this method is the fact that it takes advantage of existing studies that have examined the impacts of collisions between astronomical objects. For instance, multiple studies have been conducted that have attempted to place constraints on the giant impact that is believed to have formed the Earth-Moon system 4.5 billion years ago (aka. the Giant Impact Hypothesis).
While such giant collisions are thought to have been common during the final stage of terrestrial planet formation (lasting for approximately 100 million years), the team focused on impacts of asteroidal or cometary bodies, which are believed to occur over the entire lifetime of an exoplanetary system. Relying on these studies, Cataldi and his colleagues were able to create models for exoplanet ejecta.
As Cataldi explained, they used the results from the impact cratering literature to estimate the amount of ejecta created. To estimate the signal strength of circumstellar dust disks created by the ejecta, they used the results from debris disk (i.e. extrasolar analogues of the Solar System’s Main Asteroid Belt) literature. In the end, the results proved rather interesting:
“We found that an impact of a 20 km diameter body produces enough dust to be detectable with current telescopes (for comparison, the size of the impactor that killed the dinosaurs 65 million years ago is though to be around 10 km). However, studying the composition of the ejected dust (e.g. search for biosignatures) is not in the reach of current telescopes. In other words, with current telescopes, we could confirm the presence of ejected dust, but not study its composition.”
Perspective view looking from an unnamed crater (bottom right) towards the Worcester Crater. The region sits at the mouth of Kasei Valles, where fierce floodwaters emptied into Chryse Planitia. Credit: ESA/DLR/FU Berlin
In short, studying material ejected from exoplanets is within our reach and the ability to study its composition someday will allow astronomers to be able to characterize the geology of an exoplanet – and thus place more accurate constraints on its potential habitability. At present, astronomers are forced to make educated guesses about a planet’s composition based on its apparent size and mass.
Unfortunately, a more detailed study that could determine the presence of biosignatures in ejecta is not currently possible, and will be very difficult for even next-generation telescopes like the James Webb Space Telescope (JWSB) or Darwin. In the meantime, the study of ejecta from exoplanets presents some very interesting possibilities when it comes to exoplanet studies and characterization. As Cataldi indicated:
“By studying the ejecta from an impact event, we could learn something about the geology and habitability of the exoplanet and potentially detect a biosphere. The method is the only way I know to access the subsurface of an exoplanet. In this sense, the impact can be seen as a drilling experiment provided by nature. Our study shows that dust produced in an impact event is in principle detectable, and future telescopes might be able to constrain the composition of the dust, and therefore the composition of the planet.”
In the coming decades, astronomers will be studying extra-solar planets with instruments of increasing sensitivity and power in the hopes of finding indications of life. Given time, searching for biosignatures in the debris around exoplanets created by asteroid impacts could be done in tandem with searchers for atmospheric biosignatures.
With these two methods combined, scientists will be able to say with greater certainty that distant planets are not only capable of supporting life, but are actively doing so!
