A key method for contextualizing climate today and into the future is to draw upon the past. Marine sediments accumulating at the bottom of the ocean serve as the only continuous archive of Earth's climate history spanning tens of millions of years. From the earliest studies of marine sediments, reconstructed changes in the inputs of sedimentary constituents such as volcanic glass, ice-rafted debris, particulates carried by rivers, desert dust, organic and inorganic remnants of organisms and biological process, and even extraterrestrial material, have been used to discern past environmental conditions. Specifically, it is the rate at which these different components of sediments from the bottom of the ocean accrue over time that can provide unique and important insight into how Earth system dynamics operated in the near and distant past. Traditional techniques for quantifying sediment mass accumulation rates (MARs) contain numerous complexities that can lead to erroneous MAR determinations. Constant flux proxies (CFPs), particularly extraterrestrial <sup>3</sup>He (<sup>3</sup>He<sub>ET</sub>) delivered in interplanetary dust particles from space, are underutilized geochemical tools that alleviate these issues as long as key assumptions can be constrained. In this perspective, we review CFP <sup>3</sup>He<sub>ET</sub> as a CFP and outline its benefit for understanding Cenozoic climate beyond the Quaternary. Ultimately, we suggest that the application of <sup>3</sup>He<sub>ET</sub> is valuable for providing the broader paleoclimate and paleoceanography communities with accurate records of Cenozoic Earth system change from a MAR perspective.