 Small satellites yield big discoveries, presented by science at NASA. Remember the old adage, big things come in small packages? NASA has updated it, in the form of CubeSats. Imagine a real working satellite that's so small, you can hold it in your hands. Just 4 inches or 10 cm across, these cubes can be expanded incrementally, depending on their specific mission objectives. Originally developed in 1999 by Cal Poly San Luis Obispo and Stanford University for education purposes, NASA has since used them for new science missions, and to test new electronics, sensors, and software that might be included on larger missions. Mike Sieblum, Chief Technologist for NASA Science Mission Directorate says, the ability to test new technology at a fraction of the cost of a larger satellite makes them invaluable. It really opens your eyes to many possibilities. Just as eye-opening is the way CubeSats are quickly unlocking new scientific data. For example, while conventional satellites have long-observed clouds and have provided estimates of the liquid precipitation they hold, they have never observed the smaller ice particles that create enormous rain clouds. The CubeSat, known as IceCube, contained a new sub-millimeter wavelength radiometer that could make a space-based measurement of the small frozen crystals that make up ice clouds. After being deployed from the International Space Station in May 2017, IceCube created a global map of ice clouds around the planet. Someday this technique may help improve long-range weather models and forecasts. Along way from Earth, Marco A and B traveled to Mars and are the only CubeSats so far to leave Earth's orbit. When the InSight mission was launched in May of 2018, the Marco A and Marco B CubeSats also began their seven-month journey to Mars. Now InSight has successfully landed on the red planet. One of Marco's roles was to help relay communications during InSight's landing process. Landing data was transmitted to the Mars Reconnaissance Orbiter, where its radio stored and forwarded results to Earth after a delay. Marco A and B acted as a bent-pipe signal relay during this critical stage of the mission to allow communication from Mars to Earth to happen in almost real time. According to Charles Norton, Special Advisor for Small Spacecraft Missions in NASA's Science Mission Directorate, another advantage of these compact cubes is they allow for very focused scientific inquiries to take place. The miniature X-ray Solar Spectrometer CubeSat, or MINX, for example, is a student project using a commercial laboratory detector in space. MINX measures the soft X-ray solar spectrum in the gap of energy coverage between two other missions, Resi and Iris. This gap region in the solar spectrum is important in the excitation of the Earth's ionosphere and of particular interest for observations of solar flares and active regions. Or consider a discovery as monumental as the origin of the universe itself. One long-standing mystery for astrophysicists is where one-third of the baryonic or ordinary matter that existed during the early formation of the universe might be found today. Scientists suspect it lies in the very hot halos of gas that surround galaxies. Halosat is a CubeSat that will examine X-rays from oxygen atoms surrounding our Milky Way to determine how much missing matter may lie in the halo of our galaxy. While small in size, CubeSats have potential to make big scientific and technological impacts on Earth and our solar system and deep into the universe. For more about other science missions, both big and small, visit science.nasa.gov.