Space cloud may hold clue to life’s origins

A chemical found in a distant space cloud looks a lot like a building block of life on Earth.

The cloud sits about 26,000 light-years away in interstellar space, a term for the gap between stars. Called Sagittarius B2, the cloud contains dust and gas — the stuff that makes up planets and stars. Scientists had identified other interesting molecules there before. But those molecules tended to have a ring shape or consisted of a straight string of atoms.

The newfound isopropyl cyanide (EYE-so-PRO-ul SIGH-ah-neid) is different. Its structure is branched. That means its atoms don’t line up straight, one after another. Instead, a single atom may connect to two or three others. These chains form branches, like in a tree, astronomers reported September 26 in Science.

Branching is a big deal to scientists. Most amino acids have a branched structure. Those molecules are the basic building block for larger molecules called proteins. And proteins are crucial to life.

Finding isopropyl cyanide suggests interstellar space may hold clues to how life started.

The discovery also supports the idea that meteorites (rocks from space that land on the ground) might have helped bring life to Earth. In the past 40 years, researchers have found dozens of amino acids in meteorites. Those molecules may form on rocks as they hurtle through space.

They also may form in distant gas clouds and then hitchhike across space. If that’s the case, then the ingredients for life aren’t unique to Earth — or even the solar system. Gas clouds may forge those ingredients. Passing space rocks may then ferry the molecules to other planets in the Milky Way — or even to other galaxies.

Finding complex molecules like isopropyl cyanide in space is tricky astronomy. As molecules vibrate and move in space, they give off energy. That energy may take the form of radio waves. Scientists on Earth can pick up those signals and identify where they came from using radio telescopes.

Arnaud Belloche and his colleagues didn’t use just one telescope when they studied Sagittarius B2. They used a whole network. Called ALMA — for Atacama Large Millimeter/submillimeter Array — it is made up of 66 radio dishes. They stare at the sky from mountains in Chile. Only 20 were running when Belloche collected data. Still, those were enough to get a good signal. Belloche is an astronomer at the Max Planck Institute for Radio Astronomy in Bonn, Germany.

The new study doesn’t prove that molecules necessary for life form in interstellar clouds, he told Science News. However, finding evidence that chemicals with a branched structure can form there is exciting, he says.

Eric Herbst agrees. An astronomer at the University of Virginia in Charlottesville, he was not involved in the study. He told Science News, “This bodes well for the presence of amino acids.”

Power Words

amino acids  Simple molecules that occur naturally in plant and animal tissues and that are the basic constituents of proteins.

astronomy    The area of science that deals with celestial objects, space and the physical universe as a whole. People who work in this field are called astronomers.

atom   The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and neutrally charged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.

chemical      A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H₂O.

galaxy  A massive group of stars bound together by gravity. Galaxies, which each typically include between 10 million and 100 trillion stars, also include clouds of gas, dust and the remnants of exploded stars.

interstellar  Between stars.

isopropyl cyanide     Also known as isobutyronitrile, it has a chemical formula of (CH₃)₂CHCN. It is very toxic. On Earth, it forms during an intermediate stage of the production of some chemicals, including some insecticides.

light-year  The distance light travels in a year, about 9.48 trillion kilometers (almost 6  trillion miles). To get some idea of this length, imagine a rope long enough to wrap around the Earth. It would be a little over 40,000 kilometers (24,900 miles) long. Lay it out straight. Now lay another 236 million more that are the same length, end-to-end, right after the first. The total distance they now span would equal one light-year.

meteor  A lump of rock or metal from space that hits the atmosphere of Earth. In space it is known as a meteoroid. When you see it in the sky it is a meteor. And when it hits the ground it is called a meteorite. 

Milky Way   The galaxy in which Earth’s solar system resides.

molecule  An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O₂), but water is made of two hydrogen atoms and one oxygen atom (H₂O).

planet  A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and it must have cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, it must be big enough to pull neighboring objects into the planet itself or to sling-shot them around the planet and off into outer space. Astronomers of the International Astronomical Union (IAU) created this three-part scientific definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU ruled that Pluto did not qualify. The solar system now consists of eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

proteins      Compounds made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells.

radio waves   Waves in a part of the electromagnetic spectrum; they are a type that people now use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals; it is also used in radar.

star  The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.

telescope    Usually a light-collecting instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses. Some, however, collect radio emissions (energy from a different portion of the electromagnetic spectrum) through a network of antennas.