Researchers looking for an alternative planet for habitation are limiting their options, as a study lead by McMaster’s René Heller suggests.
Heller’s paper says that scientists who only search for Earth-like planets may be missing out on finding habitable planets that are not like Earth.
Heller is a member of the university’s Department of Physics and Astronomy and the lead author of a thought-provoking paper recently published in Astrobiology titled ‘Superhabitable Worlds’.
A seed germinated in Heller’s mind while perusing the livechat that accompanied a stream of an AbGradCon talk in 2012. It was during the chat that he noticed John Armstrong of Utah’s Weber State University asking if anyone thought that certain circumstances could make an Earth-like planet even more habitable than Earth itself.
“I thought about it for weeks and it somehow turned into a paper. I later invited John Armstrong, who asked the question, to join as co-author,” Heller recounted from his office in the Arthur Bourns Building.
The resulting work refutes Peter Ward’s and Donald Brownlee’s Rare Earth hypothesis, which argues that an Earth-like planet is necessary for extra-terrestrial life to subsist and that these planets may not exist.
Heller said he and his co-author were motivated by the lack of scholarship sharing their view that Earth is probably not the most likely place in the universe to be inhabited.
“All I found was literature proposing that there could be other forms of life.”
To address this oversight, the two academics explored the idea that Earth may only be barely habitable compared to other planets since it exists at “the very inner edge of the solar habitable zone,” and is consequently “literally marginally habitable because it just scrapes the edge of the solar habitable zone,” Heller added with a laugh.
To highlight the difference, Heller says they came up with a set of bodily characteristics that prospective superhabitable planets might possess.
The list is extensive, but some of the characteristics include: total surface area, plate tectonics, magnetic shielding, surface temperature, biological diversification and age.
“The most important aspect to consider is that these superhabitable planets will be terrestrial, meaning earth-like in composition, but slightly more massive than Earth, maybe two to three times the mass of the Earth.”
Despite the fact that a search for such planets is currently limited by technology, the paper already pinpoints a place to start once the means are available.
According to the report, a star named Alpha Centauri B is a member of the nearest stellar system to the Sun and is purported to host an Earth-mass planet, which is so close the star that it is rendered inhabitable.
“This star is interesting because it is slightly older than the Sun, which is a pro because its planets may have been inhabited earlier than Earth has…I think it will take maybe a decade or before these two to three Earth-mass planets, if they existed, could be discovered in the stellar habitable zone.”
NASA’s introduction of the James Webb telescope in 2018 could be helpful in characterizing of the planets if they cross the stellar disc once per orbit as it could detect the chemical imprints in the atmospheres of those worlds, Heller noted.
The open-minded hypothesis has gained traction amongst his scientific peers, says Heller, with most being amenable to the idea.
When asked if a migration from Earth is in the cards should conditions further deteriorate, Heller said, “Nothing is impossible…it might be an option. Not today, not in a thousand years, but maybe in a million years.”