EPSC 2012: Slow-moving rocks improve odds that life crashed to Earth from space
September 24, 2012

Slow-moving rocks improve odds that life crashed to Earth from space

Ref. PN: EPSC12/06

Microorganisms that crashed to Earth embedded in the fragments of distant planets might have been the sprouts of life on this one, according to new research presented at the European Planetary Sciences Congress (EPSC) on 25 September.

The researchers report that under certain conditions there is a high probability that life came to Earth — or spread from Earth to other planets — during the Solar System’s infancy when Earth and its planetary neighbours orbiting other stars would have been close enough to each other to exchange lots of solid material.

The findings provide the strongest support yet for lithopanspermia, the hypothesis that basic life forms are distributed throughout the Universe via meteorite-like planetary fragments cast forth by disruptions such as volcanic eruptions and collisions with objects such as asteroids. Eventually, another planetary system’s gravity traps these roaming rocks, which can result in a mingling that transfers any living cargo.

Previous research on this possible phenomenon suggested that the speed at which objects hurtle through space made the chance of them being captured by another planet very small. However, this new research, based on computer simulations of the star cluster our Sun was born in, suggests that a process called weak transfer, in which solid objects can gradually meander out of the orbit of one object and into another, greatly increase the odds that this process could have happened.

The research is based on principles of weak transfer developed by mathematician Edward Belbruno (Princeton University), and is presented at EPSC by his collaborator Amaya Moro-Martín (Centro de Astrobiología and Princeton University). Belbruno first demonstrated weak transfer in 1991 when guiding the Hiten probe to the Moon using minimal amounts of fuel.

“Our work says the opposite of most previous work,” says Belbruno. “It says that lithopanspermia might have been very likely, and it may be the first paper to demonstrate that. If this mechanism is true, it has implications for life in the universe as a whole. This could have happened anywhere.”

The team noted that low velocities offer very high probabilities for the exchange of solid material via weak transfer, and also found that the timing of such an exchange could be compatible with the actual development of the Solar System, as well as with the earliest known emergence of life on Earth.

The researchers report that the Solar System and its nearest planetary-system neighbour could have swapped rocks at least 100 trillion times well before the Sun struck out from its native star cluster. Furthermore, existing rock evidence shows that basic life forms could indeed date from the Sun’s birth cluster days — and have been hardy enough to survive an interstellar journey and eventual impact.

“The conclusion from our work,” Moro-Martín says, “is that the weak transfer mechanism makes lithopanspermia a viable hypothesis because it would have allowed large quantities of solid material to be exchanged between planetary systems, and involves timescales that could potentially allow the survival of microorganisms embedded in large boulders.”

The study shows that exchange of material between different planetary systems is likely, but it stops short when the solid matter is captured by the second planetary system. For lithopanspermia to actually take place, the material needs to land on an Earth-like planet where life could flourish.

“The study of the probability of landing on a terrestrial planet is work that we now know is worth doing because large quantities of solid material originating from the first planetary system may be trapped by the second planetary system, waiting to land on a terrestrial planet,” says Moro-Martín. “Our study does not prove lithopanspermia actually took place, but it indicates that it is an open possibility.”

As well as presenting to the EPSC, the team’s research is detailed in a paper entitled, “Chaotic Exchange of Solid Material between Planetary Systems: Implications for Lithopanspermia,” published in the 12 September issue of the journal Astrobiology.

A longer version of this story is available from the press office at Princeton University.

IMAGES

A: Weak transfer
Researchers have used a low-velocity process called weak transfer to provide the strongest support yet for “lithopanspermia,” the idea that the microorganisms that sprout life came to Earth — or spread from Earth to other developing planets — via collisions with meteorite-like planetary fragments. Under weak transfer, a slow-moving planetary fragment meanders into the outer edge of the gravitational pull, or weak stability boundary, of a planetary system. The system has only a loose grip on the fragment, meaning the fragment can escape and be propelled into space, drifting until it is pulled in by another planetary system. Credit: Amaya Moro-Martín

B: Timeline
belbruno timeline The researchers suggest that ideal conditions for lithopanspermia in the sun’s birth cluster, in the solar system and on Earth overlapped for several hundred million years (blue shaded area). Rock evidence suggests that the Earth (bottom line) contained surface water during a period when the relative velocities between the sun and its closest cluster neighbors (top line) were small enough to allow weak transfer to other planetary systems, and when the solar system (middleline) experienced high meteorite activity within the sun’s weak gravitational boundary. If life arose on Earth shortly after surface water was available, life could have journeyed from Earth to another habitable world during this time, or vice versa if life had an early start in another planetary system. Credit: Amaya Moro-Martín

C: Star cluster
star-cluster pismis24The Sun is thought to have formed in a cluster of other stars around 4.5 billion years ago. Newly born star clusters like Pismis 24 (pictured) may be similar to the environment in which the Sun spent in its early years. Much closer to its neighbours than it is now, the nascent Solar System probably exchanged material with other planetary systems, and it is possible that early life could have spread between these neighbouring planetary systems.
http://www.spacetelescope.org/images/heic0619a/
Credit: NASA, ESA and Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain).

SCIENCE CONTACTS:

Amaya Moro-Martín
Dr Moro-Martín can be contacted through the EPSC Press Office from 24-28th September

PRESS CONTACTS:

Morgan Kelly
Princeton University
Email: mgnkelly@Princeton.EDU

Anita Heward
EPSC 2012 Press Officer
Europlanet RI
Mob: +44 7756 034243
Email: anita.heward@europlanet-eu.org

EPSC Press office (24-28 September only)
Tel: +34 91 722 3020 (English enquiries)
Tel: +34 91 722 3021 (Spanish enquiries)
Fax: +34 91 722 3022

FURTHER INFORMATION

EUROPEAN PLANETARY SCIENCE CONGRESS 2012

The European Planetary Science Congress (EPSC) is the major European meeting on planetary science and attracts scientists from Europe and around the World. The 2012 programme includes more than 50 sessions and workshops. The EPSC has a distinctively interactive style, with a mix of talks, workshops and posters, intended to provide a stimulating environment for discussion.

This year’s meeting will take place at the IFEMA-Feria de Madrid, Spain, from Sunday 23 September to Friday 28 September 2012. EPSC 2012 is organised by Europlanet, a Research Infrastructure funded under the European Commission’s Framework 7 Programme, in association with the European Geosciences Union, with the support of the Centro de Astrobiología of Spain’s Instituto Nacional de Técnica Aeroespacial (CAB-INTA).

Details of the Congress and a full schedule of EPSC 2012 scientific sessions and events can be found at the official website: http://www.epsc2012.eu/

EUROPLANET

The Europlanet Research Infrastructure is a major (€6 million) programme co-funded by the European Union under the Seventh Framework Programme of the European Commission.

The Europlanet Research Infrastructure brings together the European planetary science community through a range of Networking Activities, aimed at fostering a culture of cooperation in the field of planetary sciences, Transnational Access Activities, providing European researchers with access to a range of laboratory and field site facilities tailored to the needs of planetary research, as well as on-line access to the available planetary science data, information and software tools, through the Integrated and Distributed Information Service. These programmes are underpinned by Joint Research Activities, which are developing and improving the facilities, models, software tools and services offered by Europlanet RI.

Europlanet Project website: www.europlanet-ri.eu
Europlanet Outreach website: www.europlanet-eu.org/outreach
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