Researchers from the University of Cambridge have unveiled a captivating discovery concerning the potential of comets to transport life’s essential molecular components to planets throughout the galaxy, particularly within closely-clustered planetary systems. This revelation offers fresh insights into the search for extraterrestrial life.
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The Significance of Comet Speed and ‘Peas in a Pod’ Systems
To facilitate the delivery of organic materials, comets must traverse space at relatively leisurely speeds, ideally below 15 kilometers per second. Beyond this threshold, the fundamental molecules required for life would disintegrate upon impact due to the accompanying high temperatures and velocity. Notably, ‘peas in a pod’ systems, where planets orbit closely together, emerge as the most viable settings for comets to travel at the appropriate speed. Within these systems, comets can effectively be passed or ‘bounced’ from one planet’s orbit to another, gradually reducing their velocity.
As comets decelerate to sufficiently low speeds, they may ultimately collide with a planet’s surface, delivering intact molecules that scientists posit as precursors to life. The research findings, published on November 15 in the Proceedings of the Royal Society A, propose these closely-clustered planetary systems as promising locales to explore for life beyond our Solar System, should cometary delivery play a pivotal role in life’s origin.
Comets: Conveyors of Prebiotic Molecules
Comets are renowned repositories of life’s building blocks, known as prebiotic molecules. For instance, analysis of samples from the Ryugu asteroid in 2022 revealed intact amino acids and vitamin B3. Comets also harbor substantial quantities of hydrogen cyanide (HCN), another critical prebiotic molecule. The robust carbon-nitrogen bonds within HCN enhance its resilience to high temperatures, potentially enabling it to survive atmospheric entry unscathed.
Richard Anslow, the study’s lead author from Cambridge’s Institute of Astronomy, elaborates, “We’re continually enhancing our understanding of exoplanet atmospheres. Consequently, we sought to identify planets where complex molecules could also be delivered by comets. It’s plausible that the molecules responsible for life on Earth originated from comets, and the same principle could hold true for planets elsewhere in the galaxy.”
The researchers do not assert that comets are indispensable for life’s inception on Earth or other celestial bodies. Instead, their objective was to delineate the conditions under which complex molecules, such as HCN, could feasibly be transported intact by comets.
Cometary Trajectories and the Influence of Solar Systems
The majority of comets within our Solar System reside in the Kuiper Belt, situated beyond Neptune’s orbit. Collisions or interactions with other Kuiper Belt objects can perturb their trajectories, propelling them closer to the Sun. Some eventually succumb to Jupiter’s gravitational pull, steering them toward the inner Solar System.
Anslow underscores the significance of aligning their investigations with planets resembling Earth. “Since Earth represents the sole known example of a life-sustaining planet, we aimed to ascertain which comets, traveling at what velocities, could deliver intact prebiotic molecules.”
Utilizing diverse mathematical modeling approaches, the researchers discerned that comets could potentially deliver life’s precursor molecules under specific circumstances. In solar systems hosting stars akin to our Sun, the target planet should possess relatively low mass, and the presence of closely-orbiting planets is advantageous. For planets around lower-mass stars, where velocities tend to be higher, neighboring planets on close orbits assume a more pivotal role in slowing down comets and safeguarding prebiotic molecules during atmospheric entry.
Within such densely-packed systems, each planet presents an opportunity to interact with and capture a comet. Anslow suggests, “This mechanism could conceivably account for the arrival of prebiotic molecules on planets.”
Nevertheless, for planets orbiting lower-mass stars, like M-dwarfs, the task becomes more formidable, particularly if the planets are sparsely spaced. Rocky planets in these configurations also contend with a greater frequency of high-velocity impacts, which could pose unique challenges to the development of life.
Implications for the Quest for Extraterrestrial Life
The implications of this research extend to the quest for extraterrestrial life. Anslow remarks, “It’s exhilarating that we can now identify the types of systems suitable for testing diverse origin scenarios. This approach complements existing studies on Earth, shedding light on the molecular pathways that led to the astounding diversity of life. Are there other planets where these pathways exist? Combining advancements in astronomy and chemistry allows us to delve into some of the most profound questions of all.”
Citation: “Can comets deliver prebiotic molecules to rocky exoplanets?” by R. J. Anslow, A. Bonsor, and P. B. Rimmer, November 15, 2023. Proceedings of the Royal Society A Mathematical Physical and Engineering Sciences. DOI: 10.1098/rspa.2023.0434
This research received support from the Royal Society and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI). Richard Anslow is affiliated with Wolfson College, Cambridge.
Frequently Asked Questions (FAQs) about Cometary Delivery
What is the main discovery in this research about comets and life’s building blocks?
The research from the University of Cambridge highlights that comets could potentially transport essential molecular components for life to planets in the galaxy, particularly within closely-clustered planetary systems.
How do comets deliver these building blocks to other planets?
Comets need to travel at relatively slow speeds, below 15 kilometers per second, to safely deliver intact molecules. They can achieve these slower speeds when passing through ‘peas in a pod’ planetary systems where planets orbit closely together. The comet essentially bounces between planets, gradually reducing its velocity until it crashes onto a planet’s surface, delivering intact molecules.
What are prebiotic molecules, and why are they significant?
Prebiotic molecules are the building blocks for life, including amino acids and other essential compounds. They are significant because they are believed to be precursors to the development of life. Comets are known to contain these prebiotic molecules, making them important in the context of the origins of life.
Could comets be responsible for life on Earth?
While the research doesn’t claim comets as the sole origin of life on Earth, it suggests they could have played a role in delivering the molecules that contributed to life’s development.
What types of planetary systems are most suitable for cometary delivery of prebiotic molecules?
For planets orbiting stars similar to our Sun, the target planet should have relatively low mass, and the presence of closely-orbiting planets is advantageous. In the case of planets around lower-mass stars, nearby planets on close orbits play a more significant role in slowing down comets and protecting prebiotic molecules.
What does this research mean for the search for extraterrestrial life?
This research provides insights into where scientists should focus their efforts when searching for extraterrestrial life. It suggests that closely-clustered planetary systems could be promising places to investigate, especially if cometary delivery is important for the origins of life on other planets.
More about Cometary Delivery
- University of Cambridge Research
- Proceedings of the Royal Society A
- Kuiper Belt
- Ryugu Asteroid Sample Analysis
- Science and Technology Facilities Council (STFC)
- UK Research and Innovation (UKRI)
- Wolfson College, Cambridge
