Thank you for signing the petition asking the Obama Administration to acknowledge an extraterrestrial presence here on Earth.
The U.S. government has no evidence that any life exists outside our planet, or that an extraterrestrial presence has contacted or engaged any member of the human race. In addition, there is no credible information to suggest that any evidence is being hidden from the public's eye.
However, that doesn't mean the subject of life outside our planet isn't being discussed or explored. In fact, there are a number of projects working toward the goal of understanding if life can or does exist off Earth. Here are a few examples:
SETI—the Search for ExtraTerrestrial Intelligence—was originally stood up with help from NASA, but has since been moved to other sources of private funding. SETI's main purpose is to act as a giant ear on behalf of the human race, pointing an array of ground-based telescopes towards space to listen for any signal from another world.
Kepler is a NASA spacecraft in Earth orbit that's main goal is to search for Earth-like planets. Such a planet would be located in the "Goldilocks" zone of a distant solar system—not too hot and not too cold—and could potentially be habitable by life as we know it. The Kepler mission is specifically designed to survey our region of the Milky Way galaxy to discover Earth-sized, rocky planets in or near the habitable zone of the star (sun) they orbit.
The Mars Science Laboratory, Curiosity, is an automobile-sized rover that NASA is launching soon. The rover's onboard laboratory will study rocks, soils, and other geology in an effort to detect the chemical building blocks of life (e.g., forms of carbon) on Mars and will assess what the Martian environment was like in the past to see if it could have harbored life.
A last point: Many scientists and mathematicians have looked with a statistical mindset at the question of whether life likely exists beyond Earth and have come to the conclusion that the odds are pretty high that somewhere among the trillions and trillions of stars in the universe there is a planet other than ours that is home to life.
Many have also noted, however, that the odds of us making contact with any of them—especially any intelligent ones—are extremely small, given the distances involved.
But that's all statistics and speculation. The fact is we have no credible evidence of extraterrestrial presence here on Earth.
Phil Larson works on space policy and communications at the White House Office of Science & Technology Policy