Researchers have located "the perfect solar system", forged without the violent collisions that made our own a hotchpotch of different-sized planets.

The system, 100 light years away, has six planets, all about the same size. They've barely changed since its formation up to 12 billion years ago.

These undisturbed conditions make it ideal for learning how these worlds formed and whether they host life.

The research has been published in the scientific journal, Nature.

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The creation of our own solar system was a violent process. As planets were forming some crashed into each other, disturbing orbits and leaving us with giants like Jupiter and Saturn alongside relatively small worlds like our own.

In the system HD110067, as astronomers have rather drily named it, things couldn't be more different.

MARK GARLICK/SCIENCE PHOTO LIBRARY

Artwork: Planet formation is typically a violent process

Not only are the planets similarly sized; in a far cry from the unrelated timing of the orbits of the planets in our own solar system, these rotate in synch.

In the time it takes for the innermost planet to go around the star three times, the next planet along gets around twice, and so on out to the fourth planet in the system. From there things change to a 4:3 pattern of relative orbit speeds for the last two planets.

This intricate planetary choreography is so precise that that the researchers have created a cyclical musical piece, akin to a Philip Glass-style composition, with notes and rhythms corresponding to each planet and their orbital periods. You can listen to some of it here:

A musical take on the 'perfect solar system'

Dr Rafael Luque, of the University of Chicago, who led the research described HD110067 as "the perfect solar system".

"It is ideal for studying how planets are created, because this solar system didn't have the chaotic beginnings ours did and has been undisturbed since its formation."

Dr Marina Lafarga-Magro, of Warwick University, said that the system was "beautiful and unique".

"It is really exciting, just seeing something that no-one has seen before," she told BBC News.

WALTER MYERS/SCIENCE PHOTO LIBRARY

Artwork: The new planets are between the size of Neptune, in the foreground, and the Earth

Over the past thirty years, astronomers have discovered thousands of star systems. But none of them are so well suited to study how planets formed. The planets' near identical size and the system's undisturbed nature are gold dust for astronomers because they make it much easier to compare and contrast them. That will help build up a picture of how they first formed and how they evolved.

The system also has a bright star which will make it easier to look for life signs in the planets' atmospheres.

All six of the new planets are what astronomers call "sub-Neptunes", which are larger than the Earth and smaller than the planet Neptune (which is four times wider than the Earth). The six newly discovered planets are between two and three times the size of Earth.

Interest in the new findings has been supercharged since the discovery in September that a sub-Neptune planet, called K2-18b, in another star system, has an atmosphere with hints of a gas that on Earth is produced by living organisms. Astronomers call this a biosignature.

NASA

Artwork: A sub-Neptune planet called k2-18b was found to have hints of life in September

Although our own solar system does not contain any sub-Neptunes, they are thought to be the most common type of planet in the galaxy. Yet astronomers know surprisingly little about these worlds.

They do not know whether they are mostly made of rock, gas or water, or critically, whether they provide conditions for life.

Finding out these details is "one of the hottest topics in the field" according to Dr Luque, adding that the discovery of HD110067 gives his team the perfect opportunity to answer that question relatively quickly.

"It could be a matter of less than ten years," he told BBC News.

"We know the planets, we know where they are, we just need slightly more time, but it will happen."

If the team's next round of observations indicates that sub-Neptunes can also support life, it greatly increases the number of possible habitable planets and therefore increases the chances of detecting signs of life on another world sooner rather than later.

NASA

Artwork: The planets were found using Nasa's TESS space telescope

The race is now on to detect biosignatures on one of the six new sub-Neptunes, or dozens of others detected by rival groups. With a battery of new telescopes with enhanced capabilities and others about to come online, many astronomers believe that we may not have too long to wait for that moment.

The planets were detected using NASA's Transiting Exoplanet Survey Satellite (TESS) and ESA's CHaracterising ExOPlanet Satellite (Cheops).

The search for life beyond Earth has largely revolved around our rocky red neighbor. NASA has launched multiple rovers over the years, with a new one currently en route, to sift through Mars’ dusty surface for signs of water and other hints of habitability.

Now, in a surprising twist, scientists at MIT, Cardiff University, and elsewhere have observed what may be signs of life in the clouds of our other, even closer planetary neighbor, Venus. While they have not found direct evidence of living organisms there, if their observation is indeed associated with life, it must be some sort of “aerial” life-form in Venus’ clouds — the only habitable portion of what is otherwise a scorched and inhospitable world. Their discovery and analysis is published today in the journal Nature Astronomy.

The astronomers, led by Jane Greaves of Cardiff University, detected in Venus’ atmosphere a spectral fingerprint, or light-based signature, of phosphine. MIT scientists have previously shown that if this stinky, poisonous gas were ever detected on a rocky, terrestrial planet, it could only be produced by a living organism there. The researchers made the detection using the James Clerk Maxwell Telescope (JCMT) in Hawaii, and the Atacama Large Millimeter Array (ALMA) observatory in Chile.

The MIT team followed up the new observation with an exhaustive analysis to see whether anything other than life could have produced phosphine in Venus’ harsh, sulfuric environment. Based on the many scenarios they considered, the team concludes that there is no explanation for the phosphine detected in Venus’ clouds, other than the presence of life.

“It’s very hard to prove a negative,” says Clara Sousa-Silva, research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “Now, astronomers will think of all the ways to justify phosphine without life, and I welcome that. Please do, because we are at the end of our possibilities to show abiotic processes that can make phosphine.”

“This means either this is life, or it’s some sort of physical or chemical process that we do not expect to happen on rocky planets,” adds co-author and EAPS Research Scientist Janusz Petkowski.

The other MIT co-authors include William Bains, Sukrit Ranjan, Zhuchang Zhan, and Sara Seager, who is the Class of 1941 Professor of Planetary Science in EAPS with joint appointments in the departments of Physics and of Aeronautics and Astronautics, along with collaborators at Cardiff University, the University of Manchester, Cambridge University, MRC Laboratory of Molecular Biology, Kyoto Sangyo University, Imperial College, the Royal Observatory Greenwich, the Open University, and the East Asian Observatory.

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A search for exotic things

Venus is often referred to as Earth’s twin, as the neighboring planets are similar in their size, mass, and rocky composition. They also have significant atmospheres, although that is where their similarities end. Where Earth is a habitable world of temperate oceans and lakes, Venus’ surface is a boiling hot landscape, with temperatures reaching 900 degrees Fahrenheit and a stifling air that is drier than the driest places on Earth.

Much of the planet’s atmosphere is also quite inhospitable, suffused with thick clouds of sulfuric acid, and cloud droplets that are billions of times more acidic than the most acidic environment on Earth. The atmosphere also lacks nutrients that exist in abundance on a planet surface.

“Venus is a very challenging environment for life of any kind,” Seager says.

There is, however, a narrow, temperate band within Venus’ atmosphere, between 48 and 60 kilometers above the surface, where temperatures range from 30 to 200 degrees Fahrenheit. Scientists have speculated, with much controversy, that if life exists on Venus, this layer of the atmosphere, or cloud deck, is likely the only place where it would survive. And it just so happens that this cloud deck is where the team observed signals of phosphine.

“This phosphine signal is perfectly positioned where others have conjectured the area could be habitable,” Petkowski says.

The detection was first made by Greaves and her team, who used the JCMT to zero in on Venus’ atmosphere for patterns of light that could indicate the presence of unexpected molecules and possible signatures of life. When she picked up a pattern that indicated the presence of phosphine, she contacted Sousa-Silva, who has spent the bulk of her career characterizing the stinky, toxic molecule.

Sousa-Silva initially assumed that astronomers could search for phosphine as a biosignature on much farther-flung planets. “I was thinking really far, many parsecs away, and really not thinking literally the nearest planet to us.”

The team followed up Greaves’ initial observation using the more sensitive ALMA observatory, with the help of Anita Richards, of the ALMA Regional Center at the University of Manchester. Those observations confirmed that what Greaves observed was indeed a pattern of light that matched what phosphine gas would emit within Venus’ clouds.

The researchers then used a model of the Venusian atmosphere, developed by Hideo Sagawa of Kyoto Sangyo University, to interpret the data. They found that phosphine on Venus is a minor gas, existing at a concentration of about 20 out of every billion molecules in the atmosphere. Although that concentration is low, the researchers point out that phosphine produced by life on Earth can be found at even lower concentrations in the atmosphere.

The MIT team, led by Bains and Petkowski, used computer models to explore all the possible chemical and physical pathways not associated with life, that could produce phosphine in Venus’ harsh environment. Bains considered various scenarios that could produce phosphine, such as sunlight, surface minerals, volcanic activity, a meteor strike, and lightning. Ranjan along with Paul Rimmer of Cambridge University then modeled how phosphine produced through these mechanisms could accumulate in the Venusian clouds. In every scenario they considered, the phosphine produced would only amount to a tiny fraction of what the new observations suggest is present on Venus’ clouds.

“We really went through all possible pathways that could produce phosphine on a rocky planet,” Petkowski says. “If this is not life, then our understanding of rocky planets is severely lacking.”

A life in the clouds

If there is indeed life in Venus’ clouds, the researchers believe it to be an aerial form, existing only in Venus’ temperate cloud deck, far above the boiling, volcanic surface.

“A long time ago, Venus is thought to have oceans, and was probably habitable like Earth,” Sousa-Silva says. “As Venus became less hospitable, life would have had to adapt, and they could now be in this narrow envelope of the atmosphere where they can still survive. This could show that even a planet at the edge of the habitable zone could have an atmosphere with a local aerial habitable envelope.”

In a separate line of research, Seager and Petkowski have explored the possibility that the lower layers of Venus’ atmosphere, just below the cloud deck, could be crucial for the survival of a hypothetical Venusian biosphere.

“You can, in principle, have a life cycle that keeps life in the clouds perpetually,” says Petkowski, who envisions any aerial Venusian life to be fundamentally different from life on Earth. “The liquid medium on Venus is not water, as it is on Earth.”

Sousa-Silva is now leading an effort with Jason Dittman at MIT to further confirm the phosphine detection with other telescopes. They are also hoping to map the presence of the molecule across Venus’ atmosphere, to see if there are daily or seasonal variations in the signal that would suggest activity associated with life.

“Technically, biomolecules have been found in Venus’ atmosphere before, but these molecules are also associated with a thousand things other than life,” Sousa-Silva says. “The reason phosphine is special is, without life it is very difficult to make phosphine on rocky planets. Earth has been the only terrestrial planet where we have found phosphine, because there is life here. Until now.”

This research was funded, in part, by the Science and Technology Facilities Council, the European Southern Observatory, the Japan Society for the Promotion of Science, the Heising-Simons Foundation, the Change Happens Foundation, the Simons Foundation, and the European Union’s Horizon 2020 research and innovation program.

To get a detailed profile of rock textures, contours, and composition, PIXL’s maps of the chemicals throughout a rock can be combined with mineral maps produced by the SHERLOC instrument and its partner, WATSON. SHERLOC – short for Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals – uses an ultraviolet laser to identify some of the minerals in the rock, while WATSON takes closeup images that scientists can use to determine grain size, roundness, and texture, all of which can help determine how the rock was formed.

Early WATSON closeups have already yielded a trove of data from Martian rocks, the scientists said, such as a variety of colors, sizes of grains in the sediment, and even the presence of “cement” between the grains. Such details can provide important clues about formation history, water flow, and ancient, potentially habitable Martian environments. And combined with those from PIXL, they can provide a broader environmental and even historical snapshot of Jezero Crater.

“What is the crater floor made out of? What were the conditions like on the crater floor?” asks Luther Beegle of JPL, SHERLOC’s principal investigator. “That does tell us a lot about the early days of Mars, and potentially how Mars formed. If we have an idea of what the history of Mars is like, we’ll be able to understand the potential for finding evidence of life.”

This data shows chemicals detected within a single rock on Mars by PIXL, one of the instruments on the end of the robotic arm aboard NASA’s Perseverance Mars rover. PIXL allows scientists to study where specific chemicals can be found within an area as small as a postage stamp.

Credit: NASA/JPL-Caltech

The Science Team

While the rover has significant autonomous capabilities, such as driving itself across the Martian landscape, hundreds of earthbound scientists are still involved in analyzing results and planning further investigations.

“There are almost 500 people on the science team,” Beegle said. “The number of participants in any given action by the rover is on the order of 100. It’s great to see these scientists come to agreement in analyzing the clues, prioritizing each step, and putting together the pieces of the Jezero science puzzle.”

That will be critical when the Mars 2020 Perseverance rover collects its first samples for eventual return to Earth. They’ll be sealed in superclean metallic tubes on the Martian surface so that a future mission could collect them and send back to the home planet for further analysis.

Despite decades of investigation on the question of potential life, the Red Planet has stubbornly kept its secrets.

“Mars 2020, in my view, is the best opportunity we will have in our lifetime to address that question,” said Kenneth Williford, the deputy project scientist for Perseverance.

The geological details are critical, Allwood said, to place any indication of possible life in context, and to check scientists’ ideas about how a second example of life’s origin could come about.

Combined with other instruments on the rover, the detectors on the arm, including SHERLOC and WATSON, could make humanity’s first discovery of life beyond Earth.

More About the Mission

A key objective for Perseverance’s mission on Mars is astrobiology, including the search for signs of ancient microbial life. The rover will characterize the planet’s geology and past climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and cache Martian rock and regolith (broken rock and dust).

Subsequent NASA missions, in cooperation with ESA (European Space Agency), would send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for in-depth analysis.

The Mars 2020 Perseverance mission is part of NASA’s Moon to Mars exploration approach, which includes Artemis missions to the Moon that will help prepare for human exploration of the Red Planet.

JPL, which is managed for NASA by Caltech in Pasadena, California, built and manages operations of the Perseverance rover.