* Astronomy

Tides Have Major Impact on Planet Habitability
Astronomers searching for rocky planets that could support life in other solar systems should look outside, as well as within, the so-called "habitable zone," University of Arizona planetary scientists say.
Planets too close to their stars are roasted. Planets too far from their stars are frozen. In between, research models show, there's a habitable zone where planet temperatures approximate Earth's. Any rocky planets in this just-right Goldilocks zone could be awash in liquid water, a requisite for life as we know it, theorists say.
New research by Brian Jackson, Rory Barnes and Richard Greenberg of UA's Lunar and Planetary Laboratory shows that tides can play a major role in heating terrestrial planets, creating hellish conditions on rocky alien worlds that otherwise might be liveable. And just the other way, tidal heat can also create conditions favourable to life on planets that would otherwise be unliveable.
 
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An international team of researchers has identified a novel place to look for life: on planets that orbit the Sun's stellar siblings.
Most of the stars in the Milky Way got their start in clouds of dust and gas that eventually formed clusters of stars. If our Sun started life in such a scenario, the cluster would most likely have drifted apart after a few hundred million of years.
But that might have been enough time for life to travel between the rocky debris surrounding each nascent star, according to a study led by astronomer Mauri Valtonen at the Turku University in Finland.

Source

Title: Minimal Energy Transfer of Solid Material Between Planetary Systems
Authors: Edward Belbruno, Amaya Moro-Martin, Renu Malhotra
(Version v2)

The exchange of meteorites among the terrestrial planets of our Solar System is a well established phenomenon that has triggered discussion of lithopanspermia within the Solar System. Similarly, could solid material be transferred across planetary systems? To address this question, we explore the dynamics of the transfer of small bodies between planetary systems. In particular, we examine a dynamical process that yields very low escape velocities using nearly parabolic trajectories, and the reverse process that allows for low velocity capture. These processes are chaotic and provide a mechanism for minimal energy transfer that yield an increased transfer probability compared to that of previously studied mechanisms that have invoked hyperbolic trajectories. We estimate the transfer probability in a stellar cluster as a function of stellar mass and cluster size. We find that significant amounts of solid material could potentially have been transferred from the early Solar System to our nearest neighbour stars. While this low velocity mechanism improves the odds for interstellar lithopanspermia, the exchange of biologically active materials across stellar systems depends greatly upon the highly uncertain viability of organisms over the timescales for transfer, typically millions of years.

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The technology needed to send a robotic probe to another solar system is far in the future at best. But one scientist says it's not too soon to start thinking about how to avoid contaminating extrasolar planets with hitchhiking microbes from Earth.

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