By Danny Freedman
Pascale Ehrenfreund was starting to get anxious about the summer.
It was only December when we met, but she was suddenly awash in the thought that the reading and thinking and preparations of the past 14 years were about to come to a head. Her mind was 520 million miles away, floating out near the orbit of Jupiter.
There in the frigid deep, the European satellite Rosetta was snoozing. Launched in 2004, Rosetta had carved a circuitous, sightseer’s path to the outer solar system, where it was put into hibernation as it coasted toward the comet it will chase this summer at 62,000 miles per hour. In November a landing craft will grab it and, like a robotic Errol Flynn, ride the comet around the sun and into history.
Rosetta’s alarm clock was set to go off in just over a month.
“After January 20,” Dr. Ehrenfreund, an astrobiologist and research professor in the Elliott School of International Affairs, said at the time, “boom—it will really be a wake-up for everybody.”
For the mission’s engineers and scientists, and for sky-watchers of all stripes, the wake-up would set in motion a spectacular and unprecedented feat of cosmic derring-do; landing on a comet has never been attempted. Rosetta already is the first satellite to venture so far from home relying exclusively on solar power, and by the time it lands this fall it also will be the first spacecraft to orbit a comet and observe it over time.
Yet the delicate orchestration of closing in on a comet and landing on its unknown surface is just the beginning for Dr. Ehrenfreund, one of the mission’s scientists, and her colleagues. The orbit will give them a front-row seat as the sun brings the comet to a boil. And the landing will offer a chance to mine an artifact from the birth of the solar system, one that has been in cold storage for billions of years.
So when Rosetta blinked back to life on Jan. 20 after two and a half years of silence—sending an A-OK that traveled 45 minutes at the speed of light to reach Earth—the European Space Agency control room erupted into cheers and hugs. Dr. Ehrenfreund, receiving word while at a government dinner in Austria, could hardly sit and went table to table sharing the news.
“But right now,” she cautioned in an email, “still 9 million kilometers to go.”
It was nonetheless a monumental start to a new year—one in which she also plans to be part of an experiment sent to the International Space Station and will settle in as the first female president of the Austrian Science Fund, her home country’s equivalent of the National Science Foundation in the United States. She also will be busy preparing to lead a space station experiment next year and, if all goes well, to land instruments on Mars in both 2018 and 2020.
It marked the start of another year of searching the stars for timeless and essential unknowns: the conditions under which the solar system was forged, the inventory of molecules in the universe, and unraveling the moment when chemistry became biology.
|Rosetta: a brief history. (Source: ESA)
We are composed of the traces of stars, cobbled together from materials they produced in life and rocketed out in their fiery deaths; “starstuff pondering the stars,” as astronomer Carl Sagan put it. And at this moment perhaps nothing in our galactic neighborhood is closer to that notion than the Rosetta spacecraft.
Both comets and asteroids are leftovers from the swirling gas and dust that formed the sun and accumulated into its surrounding planets, but comets are the “more pristine” artifacts, says Dr. Ehrenfreund.
While asteroids are rock or metal and reside mostly in an asteroid belt between Mars and Jupiter, comets are so-called dirty snowballs, conglomerations of ice, gas, and dust that were flung beyond the planets to the cold outer reaches of the solar system. Cometary ice has preserved easily vaporized elements that asteroids lost long ago. “Asteroids,” she says, “have just had a rougher life.”
Scientists think that comets may have brought water and the molecular ingredients of life to a young Earth, or added to what was already here. Carbon, for instance, is the basis of biology as we know it, and the comets and asteroids that pummeled the planet for hundreds of millions of years delivered it by the truckload: perhaps a million tons each year, by one estimate. That barrage of impacts helped make the Earth inhospitable at the time, Dr. Ehrenfreund says, but may have sown the seeds of life, which arose fairly soon afterward, some 3.5 billion years ago.
“We don’t know what the early Earth did with all this material. We can’t prove it, but we can research what is possible,” she says.
Whether the necessary ingredients were imported from space or homegrown, or both, “the fact that you get this prêt-à-porter with asteroids and comets, you cannot ignore that,” she says. “So that’s why we need to know the composition of those objects.”
Through Earth-bound observations and satellite missions, scientists so far have been able to discern a lot about comets: from their orbital paths, to the nature of their icy nuclei (which are among the darkest objects in the universe) and of the jets of gas and dust that in some comets form the characteristic haze, or coma, around the nucleus and a tail, which can streak across millions of miles.
Satellites have conducted observational flybys, collected samples of escaping dust and gas, and even smashed into one comet with a coffee table-size probe. Dozens of molecules have been identified in comets, including one type of amino acid—chemicals that are the building blocks of proteins, which drive essential functions for life on Earth.
All of these missions have had “an incredible impact on increasing our knowledge,” says Dr. Ehrenfreund. “But it is not a piece of the nucleus.”
In that sense, everything that the Rosetta mission finds on the comet stands to be something of a breakthrough, whether it reveals molecules that had gone undetected—or had changed chemically by the time they were found off the comet—or simply confirms and quantifies what was thought to be there.
Studying a comet from the surface also could provide unparalleled insight into its internal structure. “Those questions about porosity and layers and dynamics between ice, gas, and rock in a comet are important to understanding what actually comes down to Earth, what survives, [and] what would help to create something new upon impact,” she says.
Rosetta’s target is comet 67P/Churyumov- Gerasimenko, which is about two and a half miles in diameter and oval-shaped. Although it used to be much deeper in space, close encounters with Jupiter over the past two centuries have gradually pulled the comet closer in, and it now swings by the sun every six and a half years.
As Rosetta chases the comet over the spring and summer and enters its orbit in August, the satellite will be studying it from a distance through a fleet of cameras, sensors, and other instruments. Among them is a microscope capable of analyzing individual grains of dust flying from the comet, which Dr. Ehrenfreund is involved with as a member of the instrument's science team.
The lander, called Philae, is expected to touch down in November and will study both the surface and below, using a drill that will plunge nearly a foot into the comet. Dr. Ehrenfreund is involved with a lander instrument that will search for complex carbon-based molecules, which could include amino acids or other organic molecules that are potentially significant to life on Earth.
The hope of the European Space Agency is that Rosetta will do for planetary science what its namesake did for the understanding of Egyptian hieroglyphic writing.
“Imagine you are reading something but you cannot understand the meaning of it because you do not know the letters, the symbols, the signs that are being used,” said Alvaro Giménez, ESA’s director of science and robotic exploration, at a news conference on wake-up day. “This is the situation we find ourselves [in] when we try to tackle the big questions about our place in the universe.”
The comet “is made out of material that is linked to the infancy of our solar system—it’s pristine, noncorrupted material, giving us information [about] the gas and dust nebula that gave birth to our entire solar system,” Dr. Giménez said.
Exploring the comet “will be like opening a window in time.”
It’s not what usually comes to mind when someone refers to leading a “double life.” Torn between studying genetics or astronomy in college, Dr. Ehrenfreund took a road less traveled: She pursued them both.
It was a decision that resulted, not surprisingly, in some missed parties. But that broad focus would position her in the late- 1980s and ’90s to jump into an emerging field at the intersection of both subjects.
After college at the University of Vienna, she followed suit with a master’s in molecular biology and a PhD in astrophysics. Only a few months separated her thesis work, which involved “extracting enzymes from the skin secretions of [African clawed] frogs,” and her PhD research, observing carbon molecules in interstellar space, she recalled in an essay in the journal Astrobiology.
|ABOVE: Along the journey to deep space, Rosetta received gravitational boosts from three swings past Earth and one past Mars, which gave the satellite a nudge—and a chance to do a little sightseeing. This image of Mars was taken in February 2007.
|BELOW: After one of its swings past Earth, in November 2007, Rosetta snapped this image of the moon, pockmarked and nestled in black. On its way out, the satellite also made close-up observations of two asteroids orbiting between Mars and Jupiter. (Both: ESA © 2007 MPS FOR OSIRIS TEAM MPS/UPD/LAM/IAA/RSSD/INTA/UPM/ DASP/IDA)
In 1999, just nine years after Dr. Ehrenfreund received her PhD, an asteroid was named in her honor—a designation that is made by an asteroid’s discoverer (in this case, a renowned asteroid-hunting team led by Dutch astronomer Cornelis Johannes van Houten) but also must be approved by an international governing committee. The citation for “9826 Ehrenfreund 2114 T-3” notes her work on cosmic dust, organic molecules, and fostering international cooperation.
“They told me it’s quite a nice object,” Dr. Ehrenfreund says. (She hasn’t actually seen it. To get a good look would require a high-powered telescope, and time slots on those are usually reserved for, well, science. “Just saying, ‘Oh, I want to see my asteroid,’ doesn’t really work.”)
By 2008 she already had become a highly cited researcher of ices and organic molecules in the vast spaces between stars. She had served as a professor of astrobiology in the Netherlands, as a scientific adviser and a committee member helping to steer the work of space agencies, and as a visiting scientist and consultant at NASA’s Jet Propulsion Laboratory in California.
She was by then also a veteran of astronomical observations from some of the world’s premier optical and radio telescopes and had served on the science teams of several space missions, from the early days of Rosetta, to experiments that exposed organic and biological materials to the space environment, to helping design an instrument for detecting organic molecules on a 2018 mission to Mars.
In 2008 she became a GW research professor of space policy and international affairs in the Elliott School’s Space Policy Institute. And although policy is a decidedly terrestrial pursuit, it’s inextricably bound in the exploration of space, from where to go and what to do, to how it’s preserved, and how any of that gets funded.
As Dr. Ehrenfreund and her co-authors write in a recent article, as members of an advisory group to the European Commission: Plans for space exploration and Earth observation “are becoming more and more technically complicated and so costly that a single nation can hardly afford to realize them.”
The sustainable way forward will be through new ideas about collaboration, Dr. Ehrenfreund and her colleagues write in a 2011 report. That means partnerships not just among today’s big-league space agencies and the up-and-comers, like China and India, but also with developing nations interested in sparking technological growth, and with people from overlapping fields, such as earth science and space law.
That paper, which Dr. Ehrenfreund co-authored as chair of the international Committee on Space Research’s Panel on Exploration, outlines a series of “stepping stone” opportunities, which include international coordination of studies into extreme environments on Earth; joining forces to defray the costs of high-priority robotic missions to bring home samples from asteroids, Mars, and other objects; and a program to support a class of increasingly sophisticated, small, lightweight, and low-cost satellites that can essentially piggyback to space aboard other missions.
She helped lead one of these missions for NASA in 2010, launching a loaf of bread-size satellite that demonstrated the capacity of so-called nanosatellites to carry out astrobiology experiments. Based on its success, she’s leading a follow-up experiment for the International Space Station, planned for next year.
It’s Dr. Ehrenfreund’s search for the ingredients and origin of life, however, that will push back into the foreground with Rosetta and her planned Mars missions. The findings might fuel something deeper, too: a theory for how it all came together.
“I also work on something that is a little outside the mainstream,” Dr. Ehrenfreund says. “I do not believe that life at the beginning was composed of the compounds which we are using now, in modern biochemistry.”
One of the prevailing theories is that the first organisms were built using ribonucleic acid, or RNA, as a precursor to the current genetic molecule, DNA—an idea known as the “RNA world.” RNA still plays a vital role in life, decoding genetic instructions for making proteins, among other things, and is made with nearly the same ingredients as DNA: a set of carbon-and-nitrogen compounds called nucleobases, sugars, and phosphates. Each of those, or their precursors, have been found in space or in meteorites (fragments of asteroids and comets that survive the fall to Earth).
But the Earth was a different place billions of years ago, and Dr. Ehrenfreund thinks the environment likely was too hostile for “very fragile molecules” like sugars and meteorite-bound amino acids.
“I think you should start very simple: What was there at the very beginning, and what could withstand the radiation, and thermal and geological activity, and could be versatile enough to be incorporated into the first protocells?” she says.
The answer, she thinks, is simpler but sturdier molecules called aromatic hydrocarbons.
These honeycomb-like chains of carbon and hydrogen atoms—“aromatic” in this case refers to a type of chemical bond— represent the largest portion of solid carbon in the universe. Among carbon-containing gas molecules, too, a group called polycyclic aromatic hydrocarbons, or PAHs, is the most abundant; on Earth they are seen when carbon-based material is burned incompletely, such as in vehicle exhaust and char-grilled meat.
The availability and robustness of these compounds have led Dr. Ehrenfreund to contemplate life’s beginnings as an “aromatic world.” In 2006 she led a team in formally making the case for it in the journal Astrobiology. The argument builds in part on an earlier hypothesis about PAHs guiding the formation of a DNA-like genetic blueprint molecule. But her team’s hypothesis goes beyond that, envisioning vital roles for PAHs and other aromatic hydrocarbons in the construction and operation of life’s other requirements, as well: energy-harvesting mechanisms and the cellular structure.
“In looking at life as we know it, or as we don’t know it, we have to follow the basic rules of the universe,” Dr. Ehrenfreund said at a NASA-organized conference that year. “We have to understand abundances and distribution. The inventory is strikingly similar everywhere.” From a carbon perspective, she said, the universe “is absolutely aromatic.”
As she works to build the case in the lab—a 2012 study found PAH derivatives helped stabilize a simulated primitive cell wall, similar to cholesterol in modern cells— she does so knowing that the unknown and perhaps never knowable details loom for any theory of life’s origin. Still, there’s much that can be done to fill in the picture. And comets, she says, remain “a big question mark.”
“Everything we can measure to help us understand the organic inventory of comets will be a big breakthrough,” she says.
|Previous missions have observed, collected bits of, and even smashed into comets. But a landing has never been attempted. The Philae lander, seen in this artist's impression, promises a new view of these icy relics of the solar system. (ESA/ATG MEDIALAB)
Aromatic hydrocarbons and amino acids will be among the complex organics the Rosetta team will look for when the lander digs into comet 67P/Churyumov- Gerasimenko. While none on their own is likely to be a smoking gun, in total they may reveal much about an ancient chemical symphony and its prospects for sparking life here—and maybe elsewhere, a prospect Dr. Ehrenfreund has not ruled out.
At that 2006 NASA conference, she closed her remarks by echoing a sobering thought from evolutionary paleobiologist Simon Conway Morris: “Life may be a universal principle, but we can still be alone.”
Her own hunch is somewhere in between endless solitude and a crowded universe.
Of the possibility for primitive life beyond Earth, she says, “we cannot exclude it whatsoever.” The universe is big place. There are hundreds of billions of galaxies, and ours alone is thought to have a similarly vast number of stars. Many of those have planets, some of which may be habitable.
But finding similar life-forms? “To have exactly the same arising somewhere else, like us humans, I would be astonished. It is difficult to reproduce all these fantastic things that happened on our planet.”
Asked whether she thinks life is out there, or if she shouldn’t say, she replies, “I hope so,” with a laugh.
“I am a scientist so I have to be correct. I cannot say there will be; I cannot say there will not be,” she says. “I would just say: It would be real fun.”