It’s time to redefine what qualifies as a planet

PLANET OR NOT? A group of planetary scientists label Pluto and many other orbs in the solar system as planets, despite the definition set down by the International Astronomical Union in 2006.

Pluto is a planet. It always has been, and it always will be, says Will Grundy of Lowell Observatory in Flagstaff, Arizona. Now he just has to convince the world of that.

For centuries, the word planet meant “wanderer” and included the sun, the moon, Mercury, Venus, Mars, Jupiter and Saturn. Eventually the moon and sun were dropped from the definition, but Pluto was included, after its discovery in 1930. That idea of a planet as a rocky or gaseous body that orbited the sun stuck, all the way up until 2006.

Then, the International Astronomical Union narrowed the definition, describing a planet as any round object that orbits the sun and has moved any pesky neighbors out of its way, either by consuming them or flinging them off into space. Pluto failed to meet the last criterion (SN: 9/2/06, p. 149), so it was demoted to a dwarf planet.

Almost overnight, the solar system was down to eight planets. “The public took notice,” Grundy says. It latched onto the IAU’s definition — perhaps a bit prematurely. The definition has flaws, he and other planetary scientists argue. First, it discounts the thousands of…

Earth’s mantle may be hotter than thought

Earth's mantle
HOT STUFF Temperatures in Earth’s mantle are higher than previously thought, results from a new experiment suggest.

Temperatures across Earth’s mantle are about 60 degrees Celsius higher than previously thought, a new experiment suggests. Such toasty temperatures would make the mantle runnier than earlier research suggested, a development that could help explain the details of how tectonic plates glide on top of the mantle, geophysicists report in the March 3 Science.

“Scientists have been arguing over the mantle temperature for decades,” says study coauthor Emily Sarafian, a geophysicist at the Woods Hole Oceanographic Institution in Massachusetts and at MIT. “Scientists will argue over 10 degree changes, so changing it by 60 degrees is quite a large jump.”

The mostly solid mantle sits between Earth’s crust and core and makes up around 84 percent of Earth’s volume. Heat from the mantle fuels volcanic eruptions and drives plate tectonics, but taking the mantle’s temperature is trickier than dropping a thermometer down a hole.

Scientists know from the paths of earthquake waves and from measures of how electrical charge moves through Earth that a boundary in the mantle exists a few dozen kilometers below Earth’s surface. Above that boundary, mantle rock can begin melting on its way up to the surface. By mimicking the extreme conditions in the deep Earth — squeezing and heating bits of mantle that erupt from undersea volcanoes or similar rocks synthesized in the lab — scientist can also determine the melting temperature of mantle rock. Using these two facts, scientists have estimated that temperatures at the boundary depth below Earth’s oceans are around 1314° C to…

Scientists Find Evidence of Earth’s Oldest Life

Researchers have discovered hints of life hundreds of millions of years earlier than previously known, according to a new study published in Nature. An international team of scientists led by University College London’s Matthew Dodd have found the oldest microfossils ever in what was once a hydrothermal vent system near Quebec, estimating they could be up to 4.3 billion years old.

Located on the eastern edge of Canada’s Hudson Bay, the Nuvvuagittuq Greenstone Belt is left over from Earth’s earliest oceanic crust. There, within the quartz layers of banded iron formations, the researchers found remains of tubes and filaments (seen attached to a clump of iron in the image below) formed by bacteria on that early crust, which was part of an ancient deep-sea hydrothermal vent network.

The bacterial remnants can be dated back at least…

Oldest microfossils suggest life thrived on Earth about 4 billion years ago

SIGNS OF LIFE In rocks left over from ancient hydrothermal vents, these microscopic tubes of hematite, an ore of iron, may be remnants of early microbes.

Tiny, iron-rich fossils exhumed from the depths of an ancient ocean could reveal the cradle of life.

These micrometer-scale structures are probably remnants of microorganisms that once lived amidst ancient hydrothermal vents, researchers suggest March 1 in Nature.

“In a nutshell, what we’ve found are the oldest microfossils on Earth,” says study coauthor Matthew Dodd, a biogeochemist at University College London. The rocks that hold the fossils came from Quebec and date to somewhere between 4.28 billion and 3.77 billion years old — when Earth was still a baby. The next oldest microfossils reported are just under 3.5 billion years old, though their validity has been debated (SN: 2/8/14, p.16).

If Dodd’s structures truly are remnants of microbes, “it’s fantastic. I love it,” says astrobiologist Martin Van Kranendonk of the University of New South Wales in Sydney. But he’s not convinced. In fact, he says, “there’s just not definitive proof that any of the textures or the minerals or features they have is unique of life.”

Claims of early life are frequently fraught with controversy. For one, says Dodd, “these are big claims — these are our origins.” And scientists studying early life typically don’t have a lot to work with. It’s not like they’re looking at dinosaur bones. In billions-of-years-old microbes, obvious cellular bits and other familiar flags of life have often been stripped away. And in Earth’s oldest rocks, extreme heat and pressure can cook and squash any remnants of life…

New solar system found to have 7 Earth-size planets

seven planets
seven planets

Astronomers have just identified a nearby solar system hosting seven Earth-sized planets. Most intriguing: Three planets that orbit its central star — known as TRAPPIST-1 — may even be within a habitable zone. That means they fall within a region that could support life as we know it. As such, these newfound worlds are good sites to focus a search for alien life.

TRAPPIST-1’s big planetary family also hints that many more cousins of Earth may exist than astronomers had thought.

“It’s rather stunning that the system has so many Earth-sized planets,” says Drake Deming. He’s an astronomer at the University of Maryland in College Park. It seems like every stable spot where a planet could be, there is an Earth-sized one. And that, he adds, “bodes well for finding habitable planets.”

Astrophysicist Michaël Gillon works at the University of Liège in Belgium. He was part of a team that last year announced they had found three Earth-sized planets around TRAPPIST-1. This dwarf star is only about the size of Jupiter. It’s also much cooler than the sun. And it’s a relative neighbor to Earth, a mere 39 light-years away in the constellation Aquarius.

Follow-up observations with the Spitzer Space Telescope and additional telescopes on the ground now show that what first had appeared to be a third planet is actually a quartet of Earth-sized ones. Three of these may be habitable.

If those planets have Earthlike atmospheres, their surfaces may even host oceans of liquid water. Or at least that’s what Gillon and his colleagues reported online February 22 in Nature. Their data also offer signs of a seventh, outermost planet.

How they spotted the new worlds

All seven planets were detected by watching how their star dims as each passes — or transits — in front of it. Scientists measured how much of the star’s light each transit blocked from Earth’s view. Knowing how big a planet would have to be to do that, the astronomer calculated that all seven must have roughly the same radius as Earth.

Those dips in starlight also showed how fast the planets orbit their star: The innermost one makes a round trip in 1.5 Earth days. The outermost one takes roughly 20 days.

The planets’ masses range from about half to 1.5 times that of Earth. To figure that out, the researchers looked at the way the six inner planets tug on each other. The mass and size data then allowed the team to calculate the planets’ densities. All of this suggested that the inner six are rocky, as Earth is.

The length of each planet’s day — how quickly it spins on its axis — may sync with its sun’s orbit. That would make the innermost planet’s day 1.5 Earth days long and the outermost one’s 20 Earth days long. That would be like Earth rotating once in 365 days…

Astronomers Find Seven ‘Earth-Like’ Planets Orbiting a Cool Star

Astronomers say they’ve discovered seven Earth-sized planets in tight orbit around a cool, dim star about 39 light-years from us—and all seven are located in the habitable zone that could potentially host life. This is the first time a planetary system oriented to this kind of star has been detected—and its discovery holds the potential to lead us to a lot more exoplanets. An international team of researchers reported their findings in a letter published today in the journal Nature.

“It’s the first time we have seven planets in this temperate zone … that can be called terrestrial,” lead author Michaël Gillon, of Belgium’s Université de Liège, said in a press briefing. “So many is really, really surprising.”

TRAPPIST-1 is an ultracool dwarf star that’s 1/80th the brightness of the Sun and similar in size to Jupiter. All seven planets in its system are within 20 percent of the size and mass of Earth, and their density measurements indicate they’re likely of rocky composition. They’re clutched by TRAPPIST-1 in tight orbits—all would fit well within the orbit of Mercury. But unlike in our solar system, where such closeness to a hot star renders life impossible, the TRAPPIST-1 planetary system, with its cool celestial heart, could potentially host liquid water and organic molecules.

The first three planets were spotted in early 2016 by some of the same researchers involved in the current findings, including Gillon. As the planets cross in front of the star during their orbits, they cause the star, which emits light in the infrared, to briefly dim. Such transits, or eclipses, provide a common way for astronomers to detect exoplanets.

Using telescopes in Chile, South Africa, Spain, the UK, and Morocco, the researchers followed up on these transit signals multiple times in 2016, most notably in late September with a 20-day, nearly continuous monitoring of the star using the Spitzer Space Telescope, currently located about 145 million miles from us in an Earth-trailing orbit around the Sun. By moving our view off the Earth, researchers were able to detect 34 separate transits. This turned out to be the result of seven planets—six in near-resonant orbit—crossing in front of their home star. (The transit of the seventh was detected only once, so the orbit of this planet, known as TRAPPIST-h, hasn’t been determined yet.)

The planets have relatively narrow surface temperature fluctuations—about 100 degrees—despite their proximity to their home star. (Compare that to Mercury, which has temperature variations of nearly 1200F.) The researchers write that three of the planets—E, F, and G—“could harbor water oceans on their surfaces,…

Microbes survived inside giant cave crystals for up to 50,000 years

Naica mine in Chihuahua, Mexico
Samples from fluid pockets in crystals inside Mexico’s Naica mine in Chihuahua revealed life-forms that may have been trapped in the minerals for up to 50,000 years.


BOSTON — Microbes found stowed inside giant crystals in caves in Chihuahua, Mexico, may have survived there for tens of thousands of years. The microorganisms, which appear to be vastly different from nearly all life-forms found on Earth, offer a good indication of how resilient life can be in extremely harsh environments, including those found on other planets.

“These organisms are so extraordinary,” astrobiologist Penelope Boston said February 17 during a news conference at the annual meeting of the American Association for the Advancement of Science. They are not close to any known genus scientists have been able to identify, said Boston, director of the NASA Astrobiology Institute in Moffett Field, Calif. Their closest relatives live in caves halfway around the world or in volcanic soils or thrive on compounds such as toluene.

For eight years, Boston and her colleagues have been studying microbes deep inside the Naica lead, silver and zinc mine. Some microorganisms were discovered trapped in fluid pockets inside massive crystals of calcium sulfate. Analysis suggests that the microbes may have been tucked away in these tiny time capsules for…

5 Strange Facts About the Planet Earth

You know what it’s like: You live somewhere all your life but never realize just how great it is until someone comes to visit. While it’s just a shame we don’t get any visitors to marvel at all the peculiarities of our home planet, here are five facts you might still appreciate.


The core of the Earth is a solid lump of nickel and iron, rotating in a sea of molten iron and nickel. This rotation functions the same way winding up a hand-held generator does, giving Earth an enormous magnetic field that extends up to 50,000 kilometers out into space. This magnetic field is crucial for life on Earth, as without it we would be exposed to the full force of the Sun’s radiation. As well as causing cancers and other radiation-aggravated conditions, the radiation’s sheer force would blow our atmosphere into space, as happened with Mercury, and to a lesser extent, Mars. Instead, charged particles are (mostly) harmlessly deflected away, giving rise to the auroras.

It’s not all good though: Any particles that hit the Earth head-on tend to get trapped in the field and can’t get out. These so-called Van Allen Radiation Belts can pose a hazard for astronauts who leave low Earth orbit.


While Earth may not be the biggest planet in the system, it is the biggest rocky planet in the solar system, and also the densest. Therefore, Earth has by far the highest surface gravity of any terrestrial object in the solar system. This is both a blessing and a curse.

The reason for the high density is the large deposits of heavy elements in the Earth’s makeup. Elements such as lead and uranium are much rarer on other worlds, which gives us a huge advantage in the amount and variety of construction materials available here on Earth. The high gravity has also demanded that humans develop the reflexes and endurance necessary to cope with such gravity, meaning we are far more durable than the potential delicately boned, sloth-like creature we could be had we evolved in low gravity.

Unfortunately, that high gravity makes Earth the worst place…

Everyone on Earth Could Live in a Single Building—In Theory

In Whittier, Alaska, an entire town is clustered inside just one high-rise building. The city’s 214 residents all live there, and it’s where the post office, police department, mayor’s office, and grocery store are located. Sure, it’s easy to see how a town of just 200 people could fit inside one building. But what would it look like if everyone in the world did?

In the latest episode of RealLifeLore, the video explainer series explores what it would look like if all 7.478 billion people in the world became neighbors. Clearly,…

Desert Facts – 75 Interesting Facts About The Desert

desert facts

Desert facts: Interesting facts about deserts. Desert biome is an ecosystem that receives minimal rainfall. While hot, dry deserts of Africa are the most popular, cold deserts for instance Antarctica is the largest desert on Earth. There are four types of deserts namely hot and dry, semiarid, coastal, and cold. Life in a desert is not easy, yet many animals and plants thrive in these extreme conditions. Let’s explore more interesting facts about deserts.

Desert facts

Desert can be found in every continent except Europe.

Large mineral deposits are often found in deserts.

Many desert animals are nocturnal i.e. they sleep during the day and come out at night as the temperatures at night are more tolerable.

Desert is formed when the mountains along the edge of the desert stop the rain from getting there.

As body fat retains heat, most desert animals adapt in such a way that they store all their fat in one area in their body. Camel stores all its body fat in its hump.

Antarctica is the world’s largest desert.

70% of Australia is classified as semi-arid, arid or desert.

Australia is the driest inhabited continent on Earth.

Atacama Desert is the largest natural supplier of Sodium Nitrate.

One third of the earth surface is covered in deserts.

Desert biome facts

Sand from the Sahara is blown to Amazon Rainforest along with the wind. It actually fertilizes at the rainforest.

Antarctica is the largest cold desert on Earth.

In six hours world’s deserts receive more energy form the sun than humans consume in a year.

Sahara is the largest hot desert on Earth.

Atacama Desert is home to the largest ground telescope in the world, ALMA.

Desert actually means an abandoned place.

20% of the Earth’s desert is covered in sand.

There are polar deserts in Arctic and Antarctic. It is a region free of ice.

A desert is an area that receives the lowest rainfall.

Deserts receive less than 40 cm of rainfall in a year.

Facts about the desert

Gobi desert in Asia is very cold.

Temperature at Sahara desert can reach up to 122 degrees Fahrenheit.

Google hires a camel to get the street view of the desert.

Every year about 46,000 square miles of…