A new technology sheds light on a long-standing mystery: How did life on Earth originate? Before life emerged on Earth, in what researchers call the prebiological stage, the atmosphere was less dense. This means that high-energy radiation from space is everywhere and ionizes molecules.
It has been hypothesized that exposure of small puddles containing urea, an organic compound crucial to the formation of nucleobases, to this intense radiation caused the conversion of urea into reaction products. These products are the building blocks of life: DNA and RNA.
But to further understand this process, scientists need to further study the mechanism behind urea ionization and reaction, as well as the reaction pathway and energy consumption.
An international collaborative team composed of corresponding author Yin Zhong, currently an associate professor at the International Center for Synchrotron Radiation Innovation and Intelligence (SRIS) at Northeastern University, and colleagues from the University of Geneva (UNIGE), ETH Zurich (ETHZ), and the University of Hamburg, revealed more information through an innovative X-ray spectroscopy method.
This technology utilizes a high-order harmonic-generating light source and a submicron liquid plane ejector, allowing researchers to examine chemical reactions occurring in liquids with unparalleled temporal precision. Most importantly, this groundbreaking method allows researchers to study the complex changes in the urea molecule at the femtosecond level, or one quadrillionth of a second.
"We have demonstrated for the first time the reaction of urea molecules after ionization. Ionizing radiation destroys the urea biomolecule. But in the process of dissipating the radiation energy, urea undergoes a dynamic process that occurs on the femtosecond time scale," Yin said.
Previous studies of molecular reactions have been limited to the gas phase. To extend this research to aqueous environments, the natural environment for biochemical processes, the team had to design a device capable of producing ultra-thin liquid jets less than one millionth of a meter thick in a vacuum. Thicker liquid streams absorb some of the X-rays, hampering measurements.
Yin, who serves as lead experimenter, believes their breakthrough not only answers how life on Earth formed. It also opened up a new avenue in the novel science of atomic chemistry. "Shorter light pulses are necessary to understand chemical reactions in real time and advance the field of attochemistry. Our method allows scientists to observe molecular movies, tracking every step of the process along the way."