Comet Impact Research Articles

Food system adaptation and maintaining trade could mitigate global famine in abrupt sunlight reduction scenarios

After a major nuclear war, volcanic eruption or asteroid or comet impact that causes an abrupt sunlight reduction scenario, agricultural yields would plummet. We analyzed a nuclear winter scenario involving the injection of 150 Tg of soot in the stratosphere using a linear optimization model with and without global food trade. We investigated the effects of loss of global food trade, some simple adaptations like rationing and storage of excess food for the coldest years, and rapid, large-scale deployment of food sources which are less dependent on present day climate (so called resilient foods) including cool tolerant crops, methane single cell protein, lignocellulosic sugar, greenhouse crops, and seaweed. In the worst case of no global food trade and no adaptations, the model predicts a global famine. However, scaling up resilient foods quickly could mitigate this for many countries. Maintaining global food trade would further alleviate pressure on local food systems, unlocking the potential to feed the entire global population. However, insufficient preparation, post-disaster conflict, or economic collapse would worsen outcomes and hinder adaptation.

Martian Impact Fracturing Pervasively Influences Habitability

AbstractOn Mars, the lack of either plate tectonics or a prominent erosional hydrological cycle since the Noachian means geological changes caused by asteroid and comet impact events have been preserved. On Earth, surviving impact‐induced fractures are localized to the relatively few preserved craters on the planet. We estimate that the shell of impact‐fractured rock on Mars (the “impact‐sphere”) could provide between 9,200 times the surface area of a Mars radius sphere and up to 100 times this value, depending on the assumptions made, as potential microbially accessible space. Although >93% of craters we consider are smaller than 10 km in diameter, they contribute only about 5% of the total fracture surface area generated by all craters, making complex craters the dominant process for potential habitat formation. Microbiological data from terrestrial impact craters suggest that these fractures could have significantly enhanced local habitability by providing pathways for fluid flow, and thus nutrients and energy. However, unlike on Earth, the geological history of Mars means that pervasive impact fractures may also have provided pathways for Hesperian and Amazonian brines to infiltrate the subsurface and locally reduce habitability. Combining the fracture data with previous microbiological observations provides testable hypotheses for Martian drilling missions.

The Impact of Cometary “Impacts” on the Chemistry, Climate, and Spectra of Hot Jupiter Atmospheres

Impacts from icy and rocky bodies have helped shape the composition of Solar System objects; for example, the Earth–Moon system, or the recent impact of comet Shoemaker–Levy 9 with Jupiter. It is likely that such impacts also shape the composition of exoplanetary systems. Here, we investigate how cometary impacts might affect the atmospheric composition/chemistry of hot Jupiters, which are prime targets for characterization. We introduce a parameterized cometary impact model that includes thermal ablation and pressure driven breakup, which we couple with the 1D “radiative-convective” atmospheric model ATMO, including disequilibrium chemistry. We use this model to investigate a wide range of impactor masses and compositions, including those based on observations of Solar System comets, and interstellar ices (with JWST). We find that even a small impactor (R = 2.5 km) can lead to significant short-term changes in the atmospheric chemistry, including a factor >10 enhancement in H2O, CO, and CO2 abundances, as well as atmospheric opacity more generally, and the near-complete removal of observable hydrocarbons, such as CH4, from the upper atmosphere. These effects scale with the change in atmospheric C/O ratio and metallicity. Potentially observable changes are possible for a body that has undergone significant/continuous bombardment, such that the global atmospheric chemistry has been impacted. Our works reveals that cometary impacts can significantly alter or pollute the atmospheric composition/chemistry of hot Jupiters. These changes have the potential to mute/break the proposed link between atmospheric C/O ratio and planet formation location relative to key snowlines in the natal protoplanetary disk.

Can humanity survive to a giant comet impact?

It is well known that giant long period comets originating from the Oort's cloud could be the most threatening celestial bodies. The warning time could indeed be very short, five years, and the kinetic energy could be sufficient for global and durable effects on Earth, killing all life forms on the surface. Humans might nevertheless be able to survive decades in underground shelters. Based on a model used to determine the minimum number of people to survive on another planet, a classification of long terms shelters is proposed, taking all needs into consideration and also the double redundancy principle. Accumulation shelters corresponds to shelters with lots of resources but a weak autonomy, and therefore a well-established limited lifetime around thirty years. Borderline shelters correspond to long term shelters with strong autonomous capacities but little margins and high risks of collapse due to misconceptions, underestimations and insufficient testing. Complete shelters correspond to ideal shelters with double redundancy for every system and also for the working capacity. Thanks to a high resilience, they could last decades, eventually saving humanity from extinction. The limits of the shelters are discussed, as well as uncertainties. Given the short warning time, it is impossible to test any shelter, and, as a consequence to avoid errors in the design of a complete shelter. The risk is indeed high that some problems are underestimated and a slow but unstoppable degradation of life conditions would lead to the death of the survivals, whatever the preparation and motivation of the survivals.

Unravelling the prebiotic origins of the simplest α-ketoacids in cometary ices: a computational investigation.

We have employed the ab initio nanoreactor (AINR) and DFT calculations to explore how the soft impact of comets entering early earth's dense atmosphere could induce chemical reactions in trapped interstellar ice components, leading to the origin of glyoxylic and pyruvic acids the simplest α-ketoacids essential for prebiotic metabolic cycles.

A Theoretical Approach to the Complex Chemical Evolution of Phosphorus in the Interstellar Medium

The study of phosphorus chemistry in the interstellar medium has become a topic of growing interest in astrobiology because it is plausible that a wide range of P-bearing molecules were introduced in the early Earth by the impact of asteroids and comets on its surface, enriching prebiotic chemistry. Thanks to extensive searches in recent years, it has become clear that P mainly appears in the form of PO and PN in molecular clouds and star-forming regions. Interestingly, PO is systematically more abundant than PN by factors typically of ∼1.4–3, independently of the physical properties of the observed source. In order to unveil the formation routes of PO and PN, in this work we introduce a mathematical model for the time evolution of the chemistry of P in an interstellar molecular cloud and analyze its associated chemical network as a complex dynamical system. By making reasonable assumptions, we reduce the network to obtain explicit mathematical expressions that describe the abundance evolution of P-bearing species and study the dependences of the abundance of PO and PN on the system’s kinetic parameters with much faster computation times than available numerical methods. As a result, our model reveals that the formation of PO and PN is governed by just a few critical reactions, and fully explains the relationship between PO and PN abundances throughout the evolution of molecular clouds. Finally, the application of Bayesian methods constrains the real values of the most influential reaction rate coefficients making use of available observational data.

Impact of a Medical Scribe Program on the Educational Trajectory of Prehealth and Underrepresented in Medicine Students.

Sparse research exists on evaluating the effects of medical scribing programs on the educational trajectory of prehealth students. This study assesses the impact of the Stanford Medical Scribe Fellowship (COMET) on its prehealth participants' educational goals, preparation for graduate training, and acceptance into health professional schools. We distributed a 31-question survey with both closed- and open-ended questions to 96 alumni. The survey collected participant demographics, self-reported underrepresented in medicine (URM) status, pre-COMET clinical experiences and educational goals, application to and acceptance at health professional schools, and perceived impact of COMET on their educational trajectory. SPSS was used to complete the analyses. The survey had a 97% (93/96) completion rate. Among all respondents, 69% (64/93) applied to a health professional school and 70% (45/64) were accepted. Among URM respondents, 68% (23/34) applied to a health professional school and 70% (16/23) were accepted. Overall acceptance rates for MD/DO and PA/NP programs were 51% (24/47) and 61% (11/18), respectively. URM acceptance rates for MD/DO and PA/NP programs were 43% (3/7) and 58% (7/12), respectively. For current or recently graduated health professional school respondents, 97% (37/38) "strongly agreed" or "agreed" that COMET helped them succeed in their training. COMET is associated with a positive impact on the educational trajectory of its prehealth participants and a higher acceptance rate into health professional schools than the national rates for both overall and URM applicants. Scribing programs may serve as pipeline development and help increase the diversity of the future health care workforce.

Decomposition of Benzene during Impacts in N2-dominated Atmospheres

Benzene is a simple neutral aromatic compound found in molecular clouds, comets, and planetary atmospheres. It has been confirmed on Jupiter, Saturn, Titan, and is expected on exoplanets. In this paper, the decomposition of benzene in a simulated asteroid or comet impact into an N2-dominated atmosphere was investigated. The impact plasma was simulated with laser-induced dielectric breakdown and the gas phase decomposition products were observed using high-resolution Fourier transform infrared spectroscopy. The gas phase decomposition products involve mainly HCN, C2H2, and smaller amounts of CH4 with yields of 3.1%–24.0%, 0–11.7%, and 0.5%–3.3%, respectively. Furthermore, in presence of water, benzene also produces CO and CO2 with yields of 2.4%–35.1% and 0.01%–4.8%, respectively. The oxidation state of the product mixture is proportional to the water content. Apart from that, a black-brownish solid phase is formed during the experiments, which makes up about 60% of the original carbon content. Our results therefore show that in anoxic N2-dominated planetary atmospheres, impacts might lead to the depletion of benzene and the formation of HCN, C2H2, and CH4 and, in the presence of water, to the formation of CO and CO2.

Modelling an Extraterrestrial Epidemic

Panspermia is the theory that life has been transported between bodies in the solar system by means of asteroid or cometary impact. Assuming that panspermia is true, and that genetically related microbial life exists outside of our planet, then it is possible that such life could pose an infectious threat to the terrestrial biosphere. We offer several assumptions of the characteristics that such life might possess and extrapolate the likely epidemiological compartment approach to be applied when attempting to model the impact of an Earthly epidemic originating from an extraterrestrial pathogen.

Science communication in the face of skepticism, populism, and ignorance: what ‘Don’t Look Up’ tells us about science denial — and what it doesn’t

‘Don’t Look Up’ tells the story of a team of astrophysicists whose efforts to warn politicians, media makers, and the public about an apocalyptic comet impact on planet Earth are undermined by fundamental skepticism toward their expertise. On the one hand, the film offers a rich portrayal of contemporary anti-science sentiments, their societal conditions, and the media and communication ecology surrounding them. But on the other hand, ‘Don’t Look Up’ ignores and exaggerates several facets of those sentiments and the communicative settings in which they spread. This commentary analyzes this contrast through a science communication lens: it scrutinizes the (mis)representation of science denial and science communication in ‘Don’t Look Up’ — and aims to inspire further debate about portrayals of anti-science phenomena and potential remedies within popular media.

Humanity extinction by asteroid impact

The risk of humanity extinction by giant asteroid impact is addressed. A 100 km sized asteroid impact may transform the Earth into an inhospitable planet, thus causing the extinction of many life forms including the human species. The exact reason for such a result remains nevertheless uncertain. Based on Moon crater history and NEA observations, the probability of a giant impact is between 0.03 and 0.3 for the next billion years. However, as the warning time would be in general relatively long, humanity could have time to settle on other planets with a high probability of success. The greatest threat could come from giant long period comets. We show that the probability of a giant comet impact is 2.2 × 10-12 for the next hundred years with a very short warning time. Many possible causes would lead to a degradation of life support and the extinction of humanity during the decades following the impact. It could be a lack of energy or important resources, other catastrophic events, conflicts and inefficient human organization and the preparatory phase could also play an important role. All in all, the extinction would be highly probable though not totally sure.

Martian Meteorites Reveal Evidence of a Large Impact

By analyzing rare Martian meteorites, researchers have uncovered a crystalline structure created by a large asteroid or comet impact that potentially affected the Red Planet’s habitability.

Assessments of Aperiodic Comet Impact Effects on Earth

Assessments of Aperiodic Comet Impact Effects on Earth

Did the Human Genetic Lineage Start with Comet Impacts at the End of the Eocene?

Did the Human Genetic Lineage Start with Comet Impacts at the End of the Eocene?

Legend descent of Ganga and similarities with impact event

Role of comets and icy asteroids in getting water to Earth is under discussion for last few decades. In the recent history, we have observed and recorded two comet impact events in the solar system. Both the impacts of solwind and Shoemaker levy-9 support the argument that the impacts by comets may be a regular feature and Earth is no exception to it. In the history of mankind, there is a strong possibility that such events were observed by various civilizations.Early settlements of ancient India observed various celestial objects like stars, constellations, planets and comets.Vedas like Rigveda, Atharvaveda refer comets as “Dhumketu”. Certain hymns of Rig Vedastrongly support the possibility of impact event being observed and recorded as eyewitness account. Reference of these celestial bodies is found in various ancient legends of India. These legends may be work of imagination based on real observations. One such legend is descent of Ganga from heaven. As per Valmiki Ramayana many aspects of this legend like its composition, appearance, descent path and effects at the time of descent have close resemblance with the impact event of a celestial body like comet. Ancient Stone carvings depicting the event provide major clue about the celestial movement and the impact event.In this paper we have used ancient description from Ramayana and Veda, and compared it with modern scientific facts and geological features of the region described in the legend.There are Multiple water bodies and lakes in the Tibet behind mount Kailash. This lake region is rich with finds like coesite, stishovite and other ultra high pressure finds that are usually associated with the impact site. These lakes play crucial role in the water cycle of Asia.Though there are lot of similarities in the legend and the available facts, as on date there is no conclusive evidence which can prove the origin of river Gangaas a result of this event as mentioned in thelegend. Thus this legend may be a result of observations mixed with belief.

Neptune’s HCl upper limit from Herschel/HIFI

Here we search for hydrogen chloride (HCl) in Neptune’s stratosphere using observations of the 1876.22 GHz J=3–2 transition from the Heterodyne Instrument for the Far-Infrared (HIFI) on Herschel. Observations comprise a 7.2 hr disc-averaged integration, originally designed to investigate stratospheric methane. Significant HCl emission was not detected. Instead, we determine upper limits using step-type abundance profiles, defined by zero deep abundance and uniform volume mixing ratio for pressures less than a transition pressure (assumed to be 0.1 or 1 mbar). These profiles are a reasonable first-order approximation for an externally sourced species; at higher pressures HCl is expected to be removed by aerosol scavenging and reactions with ammonia. The 3σ upper limits are <0.70 parts per billion (ppb) for a 0.1 mbar transition pressure and <0.076 ppb for a 1 mbar transition pressure. These upper limits are the most stringent to date and are consistent with current estimates of interplanetary dust particle flux and the hypothesis that Neptune experienced a large comet impact in the past 1000 years.

Against the Nuclear Option: Planetary Defence Under International Space Law

States have grown increasingly concerned with the risk of a meteor or comet impact. Some States and international law scholars advocate using a nuclear weapon to destroy or deflect an incoming space object. This article argues that the use of nuclear weapons for planetary defence purposes is legally dubious. Planetary defence, nuclear weapons, international treaties, customary international law, non-proliferation

Unusual Lessons Learned from the SL9 Radio Observations and their Potential Consequences to Earth's Radiation Belts

AbstractMotivated by the editor's request to write a Radio Science paper as part of the AGU Grand Challenge series, we decided to use our work on radio observations of the 1994 impact of comet D/Shoemaker‐Levy 9 (SL9) on Jupiter. Our intention is to relate this work to potential consequences for Earth. The scenario being considered is an asteroid on a direct impact path to Earth, and the consequences of shattering it into pieces small enough to not hit Earth's surface. Such fragments would explode in the atmosphere, and because there are numerous such explosions, the ionosphere and trapped radiation (van Allen) belts might be significantly modified, as occurred with SL9.

Assessing the Contributions of Comet Impact and Volcanism Toward the Climate Perturbations of the Paleocene‐Eocene Thermal Maximum

AbstractThe Paleocene‐Eocene Thermal Maximum is marked by a prominent negative carbon‐isotope excursion, reflecting the injection of thousands of gigatons of isotopically light carbon into the atmosphere. The sources of the isotopically light carbon remain poorly constrained. Utilizing a multiproxy geochemical analysis (osmium isotopes, mercury, sulfur, and platinum group elements) of two Paleocene‐Eocene boundary records, we present evidence that a comet impact and major volcanic activity likely contributed to the environmental perturbations during the Paleocene‐Eocene interval. Additionally, Earth system model simulations indicate that stratospheric sulfate aerosols, commensurate with the impact magnitude, were likely to have caused transient cooling and reduced precipitation.

Explosive interaction of impact melt and seawater following the Chicxulub impact event

Abstract The impact of asteroids and comets with planetary surfaces is one of the most catastrophic, yet ubiquitous, geological processes in the solar system. The Chicxulub impact event, which has been linked to the Cretaceous-Paleogene (K-Pg) mass extinction marking the beginning of the Cenozoic Era, is arguably the most significant singular geological event in the past 100 million years of Earth’s history. The Chicxulub impact occurred in a marine setting. How quickly the seawater re-entered the newly formed basin after the impact, and its effects of it on the cratering process, remain debated. Here, we show that the explosive interaction of seawater with impact melt led to molten fuel–coolant interaction (MFCI), analogous to what occurs during phreatomagmatic volcanic eruptions. This process fractured and dispersed the melt, which was subsequently deposited subaqueously to form a series of well-sorted deposits. These deposits bear little resemblance to the products of impacts in a continental setting and are not accounted for in current classification schemes for impactites. The similarities between these Chicxulub deposits and the Onaping Formation at the Sudbury impact structure, Canada, are striking, and suggest that MFCI and the production of volcaniclastic-like deposits is to be expected for large impacts in shallow marine settings.