I believe this is Manifold: Space by Stephen Baxter. The blurb is vague, but as I recall from reading the book more than a decade ago, the things that look like they match up ("...beyond humanity itself", "...Moon, Venus, even Mars once thrived with life...", "...Japanese scientist Nemoto...") do match up with the OP's description.
The year is 2020. Fueled by an insatiable curiosity, Reid Malenfant
ventures to the far edge of the solar system, where he discovers a
strange artifact left behind by an alien civilization: A gateway that
functions as a kind of quantum transporter, allowing virtually
instantaneous travel over the vast distances of interstellar space.
What lies on the other side of the gateway? Malenfant decides to find
out. Yet he will soon be faced with an impossible choice that will
push him beyond terror, beyond sanity, beyond humanity itself.
Meanwhile on Earth the Japanese scientist Nemoto fears her worst
nightmares are coming true. Startling discoveries reveal that the
Moon, Venus, even Mars once thrived with life?life that was snuffed
out not just once but many times, in cycles of birth and destruction.