Researchers say comets may have delivered molecules for life on Earth at the perfect speed.

A new study suggests that the arrangement of planets in the Solar System might have played a crucial role in fostering life on Earth. 

Comets, believed to carry essential organic molecules for life, face destruction from high-impact strikes. 

The team calculated comet speeds and found that when neighbouring planets are closely situated, they can influence comet orbits, slowing them down. 

This facilitates a gentler collision with planets like Earth, allowing vital molecules for life to survive. 

While this scenario is more favourable for planets around sun-like stars, it may also apply to smaller stars, the researchers note.

Cometary impacts on early Earth's surface could potentially supply complex organic molecules crucial for life's origins. For success, low-velocity impacts are essential, requiring careful consideration of planetary conditions. 

The researchers used numerical experiments to explore the potential of cometary impacts to deliver life-building molecules to rocky exoplanets. 

Their findings indicate that low-velocity impacts are more likely for planets around sun-like stars, with tightly packed planetary systems around high-mass stars enhancing the intact delivery of complex organic molecules.

The study predicts correlations between biosignatures and decreasing planetary mass, increasing stellar mass, and decreasing planetary separation in tightly packed systems. 

The researchers demonstrated analytically and numerically that low-velocity impacts onto Earth-like planets are possible around sun-like stars but improbable around M-dwarf stars. 

The presence of multiple planets between the habitable zone and snow line can significantly reduce minimum impact velocity, irrespective of stellar mass. 

The study emphasises the sensitivity of impact velocity distributions to stellar mass and planetary architecture, highlighting the potential for more low-velocity impacts in tightly packed systems around higher-mass stars.

The full study is accessible here.