Greater focus needed on how existing international law can prevent the increasing militarisation of outer space
UNIVERSITY OF EXETER
There is a pressing need for countries and international organisations to understand better how existing international law can help them address serious concerns about the militarisation of outer space, a new study says.
Space is an increasingly militarized domain, with the potential to be a source and place of armed conflict. Nations are testing anti-satellite (‘ASAT’) weapons and satellites are potentially attractive targets during armed conflict.
The new study, by Dr Chris O’Meara from the University of Exeter Law School, examines how the jus ad bellum, which is a body of law that regulates when states may lawfully use force, applies to ASAT weapons and to the right of states to use them in space. The study argues that jus ad bellum regulation of ASAT technologies addresses state concerns regarding protecting satellites and other space assets and avoiding conflict in space. It says a clearer understanding of this body of law will help decision makers and military planners avoid lawful acts of self-defence being characterized as unlawful.
Dr O’Meara said: “Space is increasingly important, militarised, and congested. States and international organisations like NATO and the UN are trying to work out how legal rules apply to space and what should happen if there’s conflict in that domain. This is not fantastical Star Wars territory; it is a necessary response to real concerns about future conflict in space. Countries are putting military weapons into space and this potential threat will continue into the future.”
“For now, it is clear we are not going to get a new weapons control treaty to respond to the fears of wars in space, so we will have to rely on existing rules from the UN Charter and customary international law and to think about how these existing rules apply above Earth. So far, there has been relatively little focus on the jus ad bellum, but my view is that we do have this existing toolkit, a body of law which applies and which sets out standards of conduct, but we need to better understand how it works in space. A better appreciation of the law is a big part of the answer.”
“In the absence of a multilateral ASAT weapons control treaty, the jus ad bellum, alongside international humanitarian law, must be regarded as an essential part of the international law framework limiting their use.”
“A clearer understanding of jus ad bellum requirements could directly address pressing international concerns regarding the weaponization of space and the fear of wars between states in that domain.”
The study says adherence to jus ad bellum helps to avoid conflict and the escalation of conflict in space and has the potential to limit ASAT weapon deployment. Compliance underpins international peace and security and safeguards space for peaceful purposes and ensuring its valuable resources continue to benefit all mankind.
ARTICLE TITLE
249 Anti-Satellite Weapons and Self-Defence: Law and Limitations
Found with Webb: a potentially habitable icy world
IMAGE:
TEMPERATE EXOPLANET LHS 1140 B MAY BE A WORLD COMPLETELY COVERED IN ICE (LEFT) SIMILAR TO JUPITER’S MOON EUROPA OR MAY BE AN ICE WORLD WITH A LIQUID SUBSTELLAR OCEAN AND A CLOUDY ATMOSPHERE (CENTRE). LHS 1140 B IS 1.7 TIMES THE SIZE OF OUR PLANET EARTH (RIGHT) AND IS THE MOST PROMISING HABITABLE ZONE EXOPLANET YET FOUND IN THE SEARCH FOR LIQUID WATER BEYOND THE SOLAR SYSTEM.
view moreCREDIT: BENOIT GOUGEON, UNIVERSITÉ DE MONTRÉAL
A international team of astronomers led by Université de Montréal has made an exciting discovery about the temperate exoplanet LHS 1140 b: it could be a promising "super-Earth" covered in ice or water.
When the exoplanet LHS 1140 b was first discovered, astronomers speculated that it might be a mini-Neptune: an essentially gaseous planet, but very small in size compared to Neptune. But after analyzing data from the James Webb Space Telescope (JWST) collected in December 2023 - combined with previous data from other space telescopes such as Spitzer, Hubble and TESS - scientists have come to a very different conclusion.
Located some 48 light-years from Earth in the constellation Cetus, LHS 1140 b appears to be one of the most promising exoplanets in its star's habitable zone, potentially harboring an atmosphere and even an ocean of liquid water. The results of this discovery by Université de Montréal astronomers are available on ArXiv and will soon be published in The Astrophysical Journal Letters.
An exoplanet in the 'Goldilocks' Zone'
LHS 1140 b, an exoplanet orbiting a low-mass red dwarf star roughly one-fifth the size of the Sun, has captivated scientists due to it being one of the closest exoplanets to our Solar System that lies within its star’s habitable zone. Exoplanets found in this “Goldilocks’ Zone” have temperatures that would allow water to exist on them in liquid form — liquid water being a crucial element for life as we know it on Earth.
Earlier this year, researchers led by Charles Cadieux, a Ph.D. student at UdeM's Trottier Institute for Research on Exoplanets (iREx) supervised by professor René Doyon, reported new mass and radius estimates for LHS 1140 b with exceptional accuracy, comparable to those of the well-known TRAPPIST-1 planets: 1.7 times the size of Earth and 5.6 times its mass.
One of the critical questions about LHS 1140 b was whether it is a mini-Neptune type exoplanet (a small gas giant with a thick hydrogen-rich atmosphere) or a super-Earth (a rocky planet larger than Earth). This latter scenario included the possibility of a so-called “Hycean world” with a global liquid ocean enveloped by a hydrogen-rich atmosphere which would exhibit a distinct atmospheric signal that could be observed using the powerful Webb Telescope.
New insights from Webb data
Through an extremely competitive process, the team of astronomers obtained valuable "drector's discretionary time" (DDT) on Webb last December, during which two transits of LHS 1140 b were observed with the Canadian-built NIRISS (Near-Infrared Imager and Slitless Spectrograph) instrument. This DDT programme is only the second dedicated to the study of exoplanets in the nearly two years of Webb’s operations, underscoring the importance and potential impact of these findings.
Analysis of these observations strongly excluded the mini-Neptune scenario, with tantalizing evidence suggesting exoplanet LHS 1140 b is a super-Earth that may even have a nitrogen-rich atmosphere. If this result is confirmed, LHS 1140 b would be the first temperate planet to show evidence of a secondary atmosphere, formed after the planet’s initial formation.
Estimates based on all accumulated data reveal that LHS 1140 b is less dense than expected for a rocky planet with an Earth-like composition, suggesting that 10 to 20 per cent of its mass may be composed of water. This discovery points to LHS 1140 b being a compelling water world, likely resembling a snowball or ice planet with a potential liquid ocean at the sub-stellar point, the area of the planet’s surface that would always be facing the system’s host star due to the planet’s expected synchronous rotation (much like the Earth’s Moon).
“Of all currently known temperate exoplanets, LHS 1140 b could well be our best bet to one day indirectly confirm liquid water on the surface of an alien world beyond our Solar System,” said Cadieux, lead author of the new study. “This would be a major milestone in the search for potentially habitable exoplanets.”
Possible presence of an atmosphere and an ocean
While it is still only a tentative result, the presence of a nitrogen-rich atmosphere on LHS 1140 b would suggest the planet has retained a substantial atmosphere, creating conditions that might support liquid water. This discovery favors the water-world/snowball scenario as the most plausible.
Current models indicate that if LHS 1140 b has an Earth-like atmosphere, it would be a snowball planet with a vast "bull’s-eye" ocean measuring about 4,000 kilometers in diameter, equivalent to half the surface area of the Atlantic Ocean. The surface temperature at the centre of this alien ocean could even be a comfortable 20 degrees Celsius.
LHS 1140 b's potential atmosphere and favorable conditions for liquid water make it an exceptional candidate for future habitability studies. This planet provides a unique opportunity to study a world that could support life, given its position in its star's habitable zone and the likelihood of its having an atmosphere that can retain heat and support a stable climate.
Several years of observation ahead
Confirming the presence and composition of LHS 1140 b's atmosphere and discerning between the snowball planet and bull’s-eye ocean planet scenarios require further observations. The research team has emphasised the need for additional transit and eclipse measurements with the Webb Telescope, focusing on a specific signal that could unveil the presence of carbon dioxide. This feature is crucial for understanding the atmospheric composition and detecting potential greenhouse gases that could indicate habitable conditions on the exoplanet.
“Detecting an Earth-like atmosphere on a temperate planet is pushing Webb’s capabilities to its limits - it’s feasible; we just need lots of observing time,” said Doyon, who is also the principal investigator of the NIRISS instrument. “The current hint of a nitrogen-rich atmosphere begs for confirmation with more data. We need at least one more year of observations to confirm that LHS 1140 b has an atmosphere, and likely two or three more to detect carbon dioxide.” According to Doyon, the Webb Telescope will likely have to observe this system at every possible opportunity for several years to determine whether LHS 1140 b has habitable surface conditions.
Given LHS 1140 b's limited visibility with Webb — a maximum of only eight visits per year are possible — astronomers will require several years of observations to detect carbon dioxide and confirm the presence of liquid water on the planet's surface.
About this study
"Transmission spectroscopy of the habitable zone exoplanet LHS 1140 b with JWST/NIRISS," by Charles Cadieux et al, was published in ArXiv on June 21, 2024 and will soon be published in Astrophysical Journal Letters. Cadieux is a doctoral student at Université de Montréal's Trottier Institute for Research on Exoplanets (iREx).
Other iREx researchers who contributed to this paper are René Doyon (UdeM), Étienne Artigau (UdeM), Olivia Lim (UdeM), Michael Radica (UdeM), Salma Salhi (UdeM), Lisa Dang (UdeM), Loïc Albert (UdeM), Louis-Philippe Coulombe (UdeM), Nicolas Cowan (McGill), David Lafrenière (UdeM), Alexandrine L’Heureux (UdeM), Caroline Piaulet-Ghorayeb (UdeM), Björn Benneke (UdeM), Neil Cook (UdeM), and Marylou Fournier-Tondreau (UdeM and University of Oxford). Additional contributors are based out of the University of Michigan, the Centre national de recherche scientifique (France), NASA Goddard Space Flight Center, the American University, McGill University, McMaster University, and the University of Toronto. Cadieux and the UdeM team acknowledge financial support from the Canadian Space Agency for this study.
ARTICLE TITLE
Transmission Spectroscopy of the Habitable Zone Exoplanet LHS 1140 b with JWST/NIRISS
Stench of a gas giant? Nearby exoplanet reeks of rotten eggs. And that’s a good thing
Astronomers sniffed out the stinky atmosphere with Webb Telescope
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CONCEPT ART OF HD 189733 B, THE CLOSEST TRANSITING HOT JUPITER TO EARTH.
view moreCREDIT: ROBERTO MOLAR CANDANOSA/JOHNS HOPKINS UNIVERISTY
An exoplanet infamous for its deadly weather has been hiding another bizarre feature—it reeks of rotten eggs, according to a new Johns Hopkins University study of data from the James Webb Space Telescope.
The atmosphere of HD 189733 b, a Jupiter-sized gas giant, has trace amounts of hydrogen sulfide, a molecule that not only gives off a stench but also offers scientists new clues about how sulfur, a building block of planets, might influence the insides and atmospheres of gas worlds beyond the solar system.
The findings are published today in Nature.
“Hydrogen sulfide is a major molecule that we didn’t know was there. We predicted it would be, and we know it’s in Jupiter, but we hadn’t really detected it outside the solar system,” said Guangwei Fu, an astrophysicist at Johns Hopkins who led the research. “We’re not looking for life on this planet because it’s way too hot, but finding hydrogen sulfide is a stepping stone for finding this molecule on other planets and gaining more understanding of how different types of planets form.”
In addition to detecting hydrogen sulfide and measuring overall sulfur in HD 189733 b’s atmosphere, Fu’s team precisely measured the main sources of the planet’s oxygen and carbon—water, carbon dioxide, and carbon monoxide.
“Sulfur is a vital element for building more complex molecules, and—like carbon, nitrogen, oxygen, and phosphate—scientists need to study it more to fully understand how planets are made and what they’re made of,” Fu said.
At only 64 light-years from Earth, HD 189733 b is the nearest “hot Jupiter” astronomers can observe passing in front of its star, making it a benchmark planet for detailed studies of exoplanetary atmospheres since its discovery in 2005, Fu said.
The planet is about 13 times closer to its star than Mercury is to the sun and takes only about two Earth days to complete an orbit. It has scorching temperatures of 1,700 degrees Fahrenheit and is notorious for vicious weather, including raining glass that blows sideways on winds of 5,000 mph.
As it did by detecting water, carbon dioxide, methane, and other critical molecules in other exoplanets, Webb gives scientists yet another new tool to track hydrogen sulfide and measure sulfur in gas planets outside the solar system.
“Say we study another 100 hot Jupiters and they're all sulfur enhanced. What does that mean about how they were born and how they form differently compared to our own Jupiter?” Fu said.
The new data also ruled out the presence of methane in HD 189733 b with unprecedented precision and infrared wavelength observations from the Webb telescope, countering previous claims about that molecule’s abundance in the atmosphere.
“We had been thinking this planet was too hot to have high concentrations of methane, and now we know that it doesn’t,” Fu said.
The team also measured levels of heavy metals like those on Jupiter, a finding that could help scientists answer questions about how a planet’s metallicity correlates to its mass, Fu said.
Less-massive giant icy planets like Neptune and Uranus contain more metals than those found in gas giants like Jupiter and Saturn, the largest planets in the solar system. The higher metallicities suggest Neptune and Uranus accumulated more ice, rock, and other heavy elements relative to gases like hydrogen and helium during early periods of formation. Scientists are testing whether that correlation also holds true for exoplanets, Fu said.
“This Jupiter-mass planet is very close to Earth and has been very well studied. Now we have this new measurement to show that indeed the metal concentrations it has provide a very important anchor point to this study of how a planet’s composition varies with its mass and radius,” Fu said. “The findings support our understanding of how planets form through creating more solid material after initial core formation and then are naturally enhanced with heavy metals.”
In coming months, Fu’s team plans to track sulfur in more exoplanets and figure out how high levels of that compound might influence how close they form near their parent stars.
“We want to know how these kinds of planets got there, and understanding their atmospheric composition will help us answer that question,” Fu said.
This research was supported by NASA through the JWST GO program.
Other authors are Luis Welbanks, Dana R. Louie, and Michael Line of Arizona State University; Drake Deming, Jegug Ih, Arjun B. Savel, Eliza M.-R. Kempton, and Matt Nixon of University of Maryland; Julie Inglis and Heather A. Knutson of California Institute of Technology; Michael Zhang of University of Chicago; Joshua Lothringer of Utah Valley University; Julianne I. Moses and Gregory Henry of Tennessee State University; Everett Schlawin of University of Arizona; David K. Sing of Johns Hopkins; and Thomas Greene of NASA Ames Research Center.
HD 189733 b has been the benchmark planet for atmospheric characterization since its discovery in 2005.
CREDIT
Roberto Molar Candanosa/Johns Hopkins University
JOURNAL
Nature
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Hydrogen sulfide and metal-enriched atmosphere for a Jupiter-mass exoplanet
ARTICLE PUBLICATION DATE
8-Jul-2024
UH OH, HUMANS THE VIRAL SPREADERS
Brigham researchers develop new way for beneficial microbes to survive extreme conditions and space exploration
The team’s formulations allow microbial therapeutics, including those used to treat gastrointestinal diseases and improve crop production, to maintain their potency and function over time despite extreme temperatures, harsh manufacturing processes
The team’s formulations allow microbial therapeutics, including those used to treat gastrointestinal diseases and improve crop production, to maintain their potency and function over time despite extreme temperatures, harsh manufacturing processes, and radiation exposure
Extremophiles, microbes that live in harsh environments such as Yellowstone’s hot springs or far beneath the ice of Antarctica, provide fascinating insights on the history and potential of life on earth and the universe beyond. Humans have used microbes to help produce food and medicine for thousands of years, but modern applications face immense challenges in ensuring that microbial products, such as probiotics, remain viable through production, transportation, and storage. Investigators from Brigham and Women’s Hospital, a founding member of the Mass General Brigham healthcare system, and MIT sought to help figure out how to send materials like probiotics into space and to better treat a variety of gastrointestinal (GI) and metabolic diseases. To do this, they developed synthetic extremophiles by mixing microbes with different materials to make them shelf-stable without refrigeration and able to withstand conditions like extreme temperatures, manufacturing processes, and even radiation encountered in space flight. Their results are published in Nature Materials.
“This ability to stabilize potential therapeutics or other interventions could be transformative in a variety of settings including health care, agriculture, and space exploration,” said corresponding author Giovanni Traverso, MD, PhD, MBBCH, a gastroenterologist in Brigham’s Division of Gastroenterology, Hepatology, and Endoscopy and MIT’s Department of Mechanical Engineering. “We have found that this can be done without the need for temperature-controlled supply chain processes, which can be very costly and limiting.”
A focus of Traverso’s lab has been making medicines more stable and enhancing their abilities to be absorbed through the GI tract. Recently, the team began investigating how to stabilize probiotics by testing a range of over-the-counter products to see if there was discrepancy between what was listed on the package and the viable material they contained. They found that many of the products contained a much lower level of active cells than was listed on the label. These findings, along with a growing need to be able to send materials like probiotics into space and to better treat a variety of GI and metabolic diseases, inspired the team to attempt to develop synthetic extremophiles.
For this study, the team tested over 2,000 material microbe combinations and found unique stabilizers for three types of bacteria and one yeast, organisms which are actively being used to treat diseases and improve crop production. The four microbes were mixed and matched with an extensive panel of ingredients from the Food and Drug Administration’s ‘generally regarded as safe’ list. These solutions were then put through manufacturing processes such as freezing, drying, milling, and wet granulation to see which ingredients helped stabilize and maximize their viability.
The team also tested for materials that maintain shelf-stability and viability at room temperature for longer periods of time, as well as after exposure to high temperatures, high pressure, solvents, and ionizing radiation. They found that these microorganisms could not only survive the extreme conditions, but they also maintained their potency and function for extended periods of time without refrigeration. Notable examples included one type of bacteria that remained functional at treating traveler’s diarrhea and another commonly used for fixing nitrogen in the soil that also remained viable.
The team will continue to develop these systems and is currently working with the Bill and Melinda Gates Foundation to investigate their potential use in women’s health and neonatal care. “This approach has the potential to influence and inform our ability to deploy very useful microbes across a range of areas,” said Traverso.
Authorship: Additional authors include Miguel Jimenez, Johanna L’Heureux, Emily Kolaya, Gary W. Liu, Kyle B. Martin, Husna Ellis, Alfred Dao, Margaret Yang, Zachary Villaverde, Afeefah Khazi-Syed, Qinhao Cao, Niora Fabian, Joshua Jenkins, Nina Fitzgerald, Christina Karavasili, Benjamin Muller, and James D. Byrne.
Disclosures: Miguel Jimenez, Giovanni Traverso, Johanna L’Heureux, and Emily Kolaya have filed a provisional patent application covering the described work. Miguel Jimenez consults for VitaKey. Complete details of all relationships for profit and not-for-profit for Giovanni Traverso can be found here.
Funding: This work is supported by the Translational Research Institute for Space Health (NNX16AO69A) and the Defense Advanced Research Projects Agency (FA8650-21-2-7120).
Paper cited: Jimenez M, et al. “Synthetic extremophiles: Species-specific formulations for microbial therapeutics and beyond.” Nature Materials, DOI: 10.1038/s41563-024-01937-6
JOURNAL
Nature Materials
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Lab-produced tissue samples
ARTICLE TITLE
Synthetic extremophiles: Species-specific formulations for microbial therapeutics and beyond.
ARTICLE PUBLICATION DATE
8-Jul-2024
COI STATEMENT
Miguel Jimenez, Giovanni Traverso, Johanna L’Heureux, and Emily Kolaya have filed a provisional patent application covering the described work. Miguel Jimenez consults for VitaKey. Complete details of all relationships for profit and not-for-profit for Giovanni Traverso can be found at https://www.dropbox.com/scl/fo/nsauubxv4xp8y39nyhs3s/ADbdnUx26edoJzkpooIywrI?rlkey=aoisodkzv8zh4n2gxwtfp4ftr&e=1&dl=0.
With Turksat 6A, Türkiye has reached a new phase in the production of satellites, says Recep Tayyip Erdogan
Gokhan Ergocun |09.07.2024 -
ISTANBUL
Turkish President Recep Tayyip Erdogan said early Tuesday that despite obstacles and restrictions, Türkiye is expanding its presence in space, referring to the country’s newly launched homegrown satellite Turksat 6A.
Turksat 6A was launched Monday at 7.30 p.m. Eastern Daylight Time (2330GMT) from Cape Canaveral Space Force Station in the US state of Florida by SpaceX's Falcon 9 rocket.
Erdogan said Türkiye also sent its Turksat 5B satellite by the same rocket two and a half years ago, adding: "We are pleased to strengthen our cooperation with Elon Musk and SpaceX in various fields."
He said Türkiye has completed more than 81% of the sub-systems and software work with domestic sources for Turksat 6A, which has importance for the country's future in the space field.
As part of its national space program, Türkiye realized its first manned space travel recently, he recalled.
With Turksat 6A, Türkiye reached a new phase in the production of satellites, Erdogan noted.
He said Turksat 6A will increase the coverage capacity of Türkiye's satellites, including countries such as India, Thailand, Malaysia and Indonesia.
With Turksat 6A, Turksat's service exports will also increase, and Türkiye will join other countries with the capability to produce their own communications satellites.
He also said it is significant that Türkiye is able to produce critical communications satellites without foreign dependence.
Satellite expected to deploy after around 35 minutes
Gokhan Ergocun |09.07.2024 - TRT
ISTANBUL
Türkiye's first homegrown communications satellite, Turksat 6A, was successfully launched from the US state of Florida by SpaceX's Falcon 9 rocket.
The launching was realized at 7.30 p.m. Eastern Daylight Time (2330GMT) on Monday from Cape Canaveral Space Force Station.
After around 35 minutes, the satellite is expected to deploy, according to SpaceX.
The 4.25-ton satellite will operate at the 42 degrees East orbital position and its service life will be 15 years in orbit.
It will cover Türkiye, Europe, North Africa, the Middle East and Asia and will serve 4.5 billion people for TV, radio and emergency communications.
- Result of 10 years of work
The project for Turksat 6A has been some 10 years in the making.
Turksat 1C, the successor of the first communications satellite, Turksat 1B, was launched in 1996, followed by Turksat 2A in 2001, Turksat 3A in 2008, Turksat 4A in 2014, Turksat 4B in 2015 and Turksat 5A and 5B in 2021.
Turkish engineers took part in Turksat’s construction of the 4A and 4B satellites as well as in the design, production and testing phases of 5A and 5B.
The indigenous Turksat 6A project was officially launched on Dec. 15, 2014, beginning with the opening of the Space Systems Assembly Integration and Test Center established at Turkish Aerospace Industries facilities in cooperation with Turksat and Türkiye’s Defense Industry Agency.
Turkish-based defense firms, the Turkish Space Agency, Aselsan, C2TECH and Turkish Aerospace Industries together with Turksat and the Scientific and Technological Research Council of Türkiye's Space Technologies Research Institute completed the satellite’s construction.
The preliminary review phase of the craft started in 2015, and the first critical review phase started the next year.
The thermal structural qualification model was completed by 2017, and the second critical review phase began in 2018, while the engineering model satellite’s construction started in 2019 and concluded in 2022.
The craft’s flight model’s initial functional and thermal vacuum tests were done the same year.
In 2023, Turksat 6A’s flight model vibration and acoustic tests as well as its shock test and fit check were done.
The craft’s tests were officially finalized in 2024, and its mass properties were measured in April, followed by its delivery to the SpaceX facility in Cape Canaveral in the US state of Florida on June 4.
By Giada Santana | Euractiv | podcast by Miriam Sáenz de Tejada and Nicoletta Ionta
Today the European Union launches a rocket into space, for the first time since the war in Ukraine began. Named Ariane 6 it symbolises a renewed hope that Europe will gain ground in the new space race. But the challenges ahead are plenty. Can Europe catch up?
In this episode, host Giada Santana and science freelance journalist Senne Starckx discuss the significance of this launch, and what it means for the future of European space competitiveness.
Building materials for water-rich planets in the early solar system
Investigations with participation by Heidelberg scientists show that later emerging small bodies brought water to the Earth
Age data for certain classes of meteorite have made it possible to gain new findings on the origin of small water-rich astronomical bodies in the early solar system. These so-called planetesimals continually supplied building materials for planets – also for the Earth, whose original material contained little water. The Earth received its actual water through planetesimals, which emerged at low temperatures in the outer solar system. Ice was available there as solid-state water – unlike with small bodies which had evolved earlier and were too hot for that, being closer to the sun. Computational models carried out by an international research team, with participation by earth scientists from Heidelberg University, have shown this on the basis of the age data, from which they were also able to read the parent bodies’ thermal evolution.
The planets of our solar system formed together with their mother star, and the Earth did likewise, emerging about 4.5 billion years ago around the sun. This happened in the habitable zone, which meant that water was able to exist in liquid form on its surface. The Earth, like other planets, also grew out of planetesimals. They emerge when large quantities of dust particles accrete in high pressure zones several thousand kilometres in diameter, and collapse under their own gravity. “These small bodies did not just supply the building materials for the planets,” explains Prof. Dr Mario Trieloff, who directs the Klaus Tschira Laboratory for Cosmochemistry at Heidelberg University’s Institute of Earth Sciences. They are also the source of the Earth’s water, the scientist adds.
The circumstances under which the planetesimals actually originated in the early solar system, and whether this was also possible for considerable periods of time, have so far not been finally clarified. Important information in this regard is supplied by the age data of certain classes of meteorites, which at some stage separated from small planets. In cooperation with colleagues from Berlin, Bayreuth and Zurich (Switzerland), the Heidelberg scientists have derived the thermal evolution and point of origin of the mother bodies from this data. They show that some of the planetesimals formed very quickly, meaning within less than two million years. In that case, they heated up so strongly that they melted and lost all volatile elements, including their water.
Other planetesimals, according to the findings of the current study, arose later at lower temperatures in the outer solar system; they were partly able to conserve their water bound up in crystals. The fact that these small bodies were also able to continually form at later stages of the solar system is, according to the scientists, due to various delaying effects counteracting the mechanisms of rapid origin, for example, collisions between dust agglomerates − the building materials of planetesimals − which prevented the rapid growth of small planets.
“The Earth accreted such small water-rich planets or their fragments in the form of asteroids or meteorites during its growth process and that is the only reason why it did not become a bone-dry planet, hostile to life,” says Dr Wladimir Neumann, first author of the study, which is based on research carried out at Heidelberg University, the Institute of Planetary Research at the German Aerospace Center and the Institute of Geodesy at TU Berlin.
Since the origin of planetesimals in extrasolar planetary systems is based on the same physical laws as in our solar system, the scientists assume that there could also be planets similar to the Earth in other regions of space. If they have received water from small bodies in the course of their evolutionary history they could meet the preconditions for the origin of life, according to Prof. Trieloff.
The research findings were published in the journal Nature Scientific Reports. Participating in the investigations were scientists from TU Berlin, the German Aerospace Center, ETH Zurich (Switzerland) and the University of Bayreuth. Funding for the research studies came from the German Research Foundation, the Klaus Tschira Foundation and the International Space Science Institute in Bern (Switzerland) and Beijing (China).
JOURNAL
Scientific Reports
ARTICLE TITLE
Recurrent planetesimal formation in an outer part of the early solar system
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