This Fourth of July, July 4, 2026, will revel in extra special fireworks. Festivities will celebrate the United States from its beginnings as a new nation to its 250th birthday. Going back just 29 years, another celebration took place, garnering such suspense and enthusiasm, it broke the newly born World Wide Web.

On July 4, 1997, the world hung breathlessly on news of the Mars Pathfinder spacecraft. The last time NASA had been to Mars, it was the 200th year of the United States, 1976, with the successful Viking Missions. Viking Missions landed on the Martian surface with parachutes and thrusters after first orbiting the planet. Pathfinder would use a cost saving and innovative strategy of heading directly into Mars’s thin atmosphere using parachutes, then deploying airbags, bouncing the lander until it could finally settle into an upright position.

In addition to that blazingly new technology, Pathfinder carried a rover, Sojourner. It was the first wheeled vehicle designed to propel itself around the surface of another planet. About the size of a microwave on a skateboard, Sojourner rolled onto the dusty desert floodplain and into history.

Demand for Sojourner’s new images was so great, the budding World Wide Web could not handle the 47 million download requests it immediately received. Celebrations continued as pictures of the Martian surface captured the world’s collective wonder for three months, three times beyond initial expectations.

Jet Propulsion Laboratories (JPL) created two rovers for the mission. Both were fully operational. Sojourner was named for Sojourner Truth, an abolitionist and women’s rights activist whose name means, traveler. After a year-long competition in which students worldwide submitted essays, Valerie Ambroise’s (age 12) choice was selected. In second place was Deepti Rohatgi’s (age 18) essay, nominating Marie Curie – the twice Nobel Prize winner, best known for discovery and research of radium.

Sojourner would fly with Pathfinder. On Earth, JPL engineers operated Marie Curie, testing movements at the same time as her Martian counterpart. Sojourner rests on Mars while Marie Curie resides at the National Air and Space Museum. Twin rovers that transformed exploration set a high bar for all missions that would follow.

While celebrating birthdays, a Fourth of July salute goes to American astronomer, Henrietta Swan Leavitt on the 158th anniversary of her birth. Leavitt’s work as one of the storied staff of women known as “computers,” hired by William Pickering of Harvard College Observatory, revolutionized how astronomers viewed and measured the universe.

Leavitt painstakingly observed thousands of images, overlaying two glass photographic plates and recording changes between exposures. Measuring dimming and brightening of Cepheid stars, her notations lead to calibrating a measurement called the “period-luminosity relation.” This created a key to measuring not just distances between stars, but galactic spans. Edwin Hubble, utilizing Leavitt’s measurements, made the astounding discovery that the Milky Way was just one galaxy in an expanding universe.

In her lifetime, Leavitt’s achievements were not given her name. She would never know the legacy of her work. But “Leavitt’s Law,” gives measurement to distances we continue to dream we will one day explore.